Stop using a special inner body for the coroutine by-move body for async closures

compiler/rustc_monomorphize/src/polymorphize.rs

@@ -127,7 +127,7 @@ fn mark_used_by_default_parameters<'tcx>(
     unused_parameters: &mut UnusedGenericParams,
 ) {
     match tcx.def_kind(def_id) {
-        DefKind::Closure => {
+        DefKind::Closure | DefKind::SyntheticCoroutineBody => {
             for param in &generics.own_params {
                 debug!(?param, "(closure/gen)");
                 unused_parameters.mark_used(param.index);