Rollup merge of #104786 - WaffleLapkin:amp-mut-help, r=compiler-errors

Use the power of adding helper function to simplify code w/ `Mutability`

r? `@compiler-errors`

compiler/rustc_symbol_mangling/src/v0.rs

@@ -622,7 +622,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
                 });
 
                 match inner_ty.kind() {
-                    ty::Str if *mutbl == hir::Mutability::Not => {
+                    ty::Str if mutbl.is_not() => {
                         match ct.kind() {
                             ty::ConstKind::Value(valtree) => {
                                 let slice =