Rollup merge of #108007 - compiler-errors:str-less-kind, r=Nilstrieb

Use `is_str` instead of string kind comparison

Split out from #107939

compiler/rustc_lint/src/non_fmt_panic.rs

@@ -146,7 +146,7 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
             // If this is a &str or String, we can confidently give the `"{}", ` suggestion.
             let is_str = matches!(
                 ty.kind(),
-                ty::Ref(_, r, _) if *r.kind() == ty::Str,
+                ty::Ref(_, r, _) if r.is_str(),
             ) || matches!(
                 ty.ty_adt_def(),
                 Some(ty_def) if Some(ty_def.did()) == cx.tcx.lang_items().string(),