Add search terms for hide and hide-env (#15017)

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Adds search terms for hide and hide-env.

Rel: #15013 

# User-Facing Changes
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crates/nu-cmd-lang/src/core_commands/hide.rs

@@ -32,6 +32,10 @@ This command is a parser keyword. For details, check:
   https://www.nushell.sh/book/thinking_in_nu.html"#
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["unset"]
+    }
+
     fn command_type(&self) -> CommandType {
         CommandType::Keyword
     }

crates/nu-cmd-lang/src/core_commands/hide_env.rs

@@ -29,6 +29,10 @@ impl Command for HideEnv {
         "Hide environment variables in the current scope."
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["unset", "drop"]
+    }
+
     fn run(
         &self,
         engine_state: &EngineState,