Revert "Make sure unmuted actors can't run on two schedulers concurrently"

This reverts commit dbfbd9a.

Reverting this because it's an incomplete fix and a proper fix will require
larger changes. Will revisit later.

Author: dipinhora

src/libponyrt/sched/scheduler.c

@@ -1488,23 +1488,10 @@ bool ponyint_sched_unmute_senders(pony_ctx_t* ctx, pony_actor_t* actor)
     {
       needs_unmuting = ponyint_actorstack_pop(needs_unmuting, &to_unmute);
 
-      // check if the actor has any messages waiting to be processed
-      // note: this must be done before the actor is unmuted to
-      // avoid a race condition
-      bool should_reschedule = !ponyint_messageq_isempty(&to_unmute->q);
-
-      // unmute actor
       ponyint_unmute_actor(to_unmute);
-
-      // only reschedule if the actor had messages waiting to be processed
-      // before we unnmuted it to ensure it cannot be concurrently
-      // scheduled on multiple scheduler threads
-      if(should_reschedule)
-      {
-        ponyint_sched_add(ctx, to_unmute);
-        DTRACE2(ACTOR_SCHEDULED, (uintptr_t)sched, (uintptr_t)to_unmute);
-        actors_rescheduled++;
-      }
+      ponyint_sched_add(ctx, to_unmute);
+      DTRACE2(ACTOR_SCHEDULED, (uintptr_t)sched, (uintptr_t)to_unmute);
+      actors_rescheduled++;
 
       ponyint_sched_start_global_unmute(ctx->scheduler->index, to_unmute);
     }