Use variable names directly in the format strings (#7906)

# Description

Lint: `clippy::uninlined_format_args`

More readable in most situations.
(May be slightly confusing for modifier format strings
https://doc.rust-lang.org/std/fmt/index.html#formatting-parameters)

Alternative to #7865

# User-Facing Changes

None intended

# Tests + Formatting

(Ran `cargo +stable clippy --fix --workspace -- -A clippy::all -D
clippy::uninlined_format_args` to achieve this. Depends on Rust `1.67`)

crates/nu-command/src/misc/tutor.rs

@@ -117,7 +117,7 @@ fn tutor(
 
         let message = format!(
             "You can find '{find}' in the following topics:\n\n{}\n\n{notes}",
-            results.into_iter().map(|x| format!("- {}", x)).join("\n")
+            results.into_iter().map(|x| format!("- {x}")).join("\n")
         );
 
         return Ok(display(&message, engine_state, stack, span));
@@ -126,7 +126,7 @@ fn tutor(
             let results = search_space.map(|s| s.0[0].to_string());
             let message = format!(
                 "This tutorial contains the following topics:\n\n{}\n\n{notes}",
-                results.map(|x| format!("- {}", x)).join("\n")
+                results.map(|x| format!("- {x}")).join("\n")
             );
             return Ok(display(&message, engine_state, stack, span));
         }