message: Fix `cargo fix --edition` on stable.
diff: @@ -857,8 +857,7 @@ impl FixArgs {
  if edition.supports_compat_lint() {
  if env::var_os(SUPPORTS_FORCE_WARN).is_some() {
  cmd.arg("--force-warn")
  - .arg(format!("rust-{}-compatibility", edition))
  - .arg("-Zunstable-options");
  + .arg(format!("rust-{}-compatibility", edition));
  } else {
  cmd.arg("-W").arg(format!("rust-{}-compatibility", edition));
  }
  