Rename misused "deprecation" to removal (#10000)

# Description
In the past we named the process of completely removing a command and
providing a basic error message pointing to the new alternative
"deprecation".

But this doesn't match the expectation of most users that have seen
deprecation _warnings_ that alert to either impending removal or
discouraged use after a stability promise.

# User-Facing Changes
Command category changed from `deprecated` to `removed`

crates/nu-command/src/default_context.rs

@@ -374,7 +374,7 @@ pub fn add_shell_command_context(mut engine_state: EngineState) -> EngineState {
             IsAdmin,
         };
 
-        // Deprecated
+        // Removed
         bind_command! {
             LetEnv,
             DateFormat,

crates/nu-command/src/lib.rs

@@ -3,7 +3,6 @@ mod conversions;
 mod date;
 mod debug;
 mod default_context;
-mod deprecated;
 mod env;
 mod example_test;
 mod experimental;
@@ -21,6 +20,7 @@ mod path;
 mod platform;
 mod progress_bar;
 mod random;
+mod removed;
 mod shells;
 mod sort_utils;
 mod strings;
@@ -32,7 +32,6 @@ pub use conversions::*;
 pub use date::*;
 pub use debug::*;
 pub use default_context::*;
-pub use deprecated::*;
 pub use env::*;
 #[cfg(test)]
 pub use example_test::test_examples;
@@ -50,6 +49,7 @@ pub use network::*;
 pub use path::*;
 pub use platform::*;
 pub use random::*;
+pub use removed::*;
 pub use shells::*;
 pub use sort_utils::*;
 pub use strings::*;

crates/nu-command/src/removed/format.rs

@@ -23,15 +23,11 @@ impl Command for SubCommand {
                 SyntaxShape::String,
                 "the desired date format",
             )
-            .category(Category::Date)
+            .category(Category::Removed)
     }
 
     fn usage(&self) -> &str {
-        "Format a given date using a format string."
-    }
-
-    fn search_terms(&self) -> Vec<&str> {
-        vec!["fmt", "strftime"]
+        "Removed command: use `format date` instead"
     }
 
     fn run(
@@ -41,7 +37,7 @@ impl Command for SubCommand {
         call: &Call,
         _input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        Err(nu_protocol::ShellError::DeprecatedCommand(
+        Err(nu_protocol::ShellError::RemovedCommand(
             self.name().to_string(),
             "format date".to_owned(),
             call.head,

crates/nu-command/src/removed/let_env.rs

@@ -20,11 +20,11 @@ impl Command for LetEnv {
                 SyntaxShape::Keyword(b"=".to_vec(), Box::new(SyntaxShape::MathExpression)),
                 "equals sign followed by value",
             )
-            .category(Category::Deprecated)
+            .category(Category::Removed)
     }
 
     fn usage(&self) -> &str {
-        "`let-env FOO = ...` is deprecated, use `$env.FOO = ...` instead."
+        "`let-env FOO = ...` has been removed, use `$env.FOO = ...` instead."
     }
 
     fn run(
@@ -34,7 +34,7 @@ impl Command for LetEnv {
         call: &Call,
         _: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        Err(nu_protocol::ShellError::DeprecatedCommand(
+        Err(nu_protocol::ShellError::RemovedCommand(
             self.name().to_string(),
             "$env.<environment variable> = ...".to_owned(),
             call.head,

crates/nu-command/src/removed/mod.rs

@@ -1,7 +1,7 @@
-mod deprecated_commands;
 mod format;
 mod let_env;
+mod removed_commands;
 
-pub use deprecated_commands::*;
 pub use format::SubCommand as DateFormat;
 pub use let_env::LetEnv;
+pub use removed_commands::*;

crates/nu-command/src/removed/removed_commands.rs

@@ -1,10 +1,10 @@
 use std::collections::HashMap;
 
-/// Return map of <deprecated_command_name, new_command_name>
-/// This covers simple deprecated commands nicely, but it's not great for deprecating
+/// Return map of <removed_command_name, new_command_name>
+/// This covers simple removed commands nicely, but it's not great for deprecating
 /// subcommands like `foo bar` where `foo` is still a valid command.
 /// For those, it's currently easiest to have a "stub" command that just returns an error.
-pub fn deprecated_commands() -> HashMap<String, String> {
+pub fn removed_commands() -> HashMap<String, String> {
     [
         ("fetch".to_string(), "http get".to_string()),
         ("post".to_string(), "http post".to_string()),

crates/nu-command/src/system/run_external.rs

@@ -295,15 +295,15 @@ impl ExternalCommand {
                 match err.kind() {
                     // If file not found, try suggesting alternative commands to the user
                     std::io::ErrorKind::NotFound => {
-                        // recommend a replacement if the user tried a deprecated command
+                        // recommend a replacement if the user tried a removed command
                         let command_name_lower = self.name.item.to_lowercase();
-                        let deprecated = crate::deprecated_commands();
-                        if deprecated.contains_key(&command_name_lower) {
-                            let replacement = match deprecated.get(&command_name_lower) {
+                        let removed_from_nu = crate::removed_commands();
+                        if removed_from_nu.contains_key(&command_name_lower) {
+                            let replacement = match removed_from_nu.get(&command_name_lower) {
                                 Some(s) => s.clone(),
                                 None => "".to_string(),
                             };
-                            return Err(ShellError::DeprecatedCommand(
+                            return Err(ShellError::RemovedCommand(
                                 command_name_lower,
                                 replacement,
                                 self.name.span,