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-pretty-hex/src/pretty_hex.rs

@@ -246,7 +246,7 @@ where
                         style.suffix()
                     )?;
                 } else {
-                    write!(writer, "{}", replacement_char,)?;
+                    write!(writer, "{replacement_char}",)?;
                 }
             }
         }