Remove workflow context lock from retry path (#808)

Author: shreyassrivatsan

internal/internal_task_handlers.go

@@ -874,13 +874,6 @@ func (w *workflowExecutionContextImpl) retryLocalActivity(lar *localActivityResu
 	if backoff > 0 && backoff <= w.GetDecisionTimeout() {
 		// we need a local retry
 		time.AfterFunc(backoff, func() {
-			w.Lock()
-			defer w.Unlock(nil)
-
-			// after backoff, check if it is still relevant
-			if w.IsDestroyed() {
-				return
-			}
 			if _, ok := w.eventHandler.pendingLaTasks[lar.task.activityID]; !ok {
 				return
 			}