Fix issue where cargo fmt --version would not display version info

Fixes 5395

In PR 5239 we switched from using `structopt` to `clap`. It seems that
the default behavior for `clap` is to override the `--version` flag,
which prevented our custom version display code from running.

The fix as outlined in clap-rs/clap#3405 was
to set `#[clap(global_setting(AppSettings::NoAutoVersion))]` to prevent
clap from setting its own default behavior for the `--version` flag.

src/cargo-fmt/main.rs

@@ -14,14 +14,15 @@ use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::str;
 
-use clap::{CommandFactory, Parser};
+use clap::{AppSettings, CommandFactory, Parser};
 
 #[path = "test/mod.rs"]
 #[cfg(test)]
 mod cargo_fmt_tests;
 
 #[derive(Parser)]
 #[clap(
+    global_setting(AppSettings::NoAutoVersion),
     bin_name = "cargo fmt",
     about = "This utility formats all bin and lib files of \
              the current crate using rustfmt."