Fix typo in -Cno-stack-check deprecation warning

The flag `--no-stack-check` does not exist:

    $ rustc --no-stack-check
    error: Unrecognized option: 'no-stack-check'. Did you mean `-C no-stack-check`?

compiler/rustc_driver_impl/src/lib.rs

@@ -1133,7 +1133,7 @@ pub fn describe_flag_categories(early_dcx: &EarlyDiagCtxt, matches: &Matches) ->
     }
 
     if cg_flags.iter().any(|x| *x == "no-stack-check") {
-        early_dcx.early_warn("the --no-stack-check flag is deprecated and does nothing");
+        early_dcx.early_warn("the `-Cno-stack-check` flag is deprecated and does nothing");
     }
 
     if cg_flags.iter().any(|x| *x == "passes=list") {