[SYCL][L0] Fix memory leak in USM prefetch.

L0 plugin increments the ref count of the dependency event twice in USM prefetch.
The fix is to remove the unnecessary retain call.

Signed-off-by: Byoungro So <[email protected]>

Author: bso-intel

sycl/plugins/level_zero/pi_level_zero.cpp

@@ -7294,11 +7294,6 @@ pi_result piextUSMEnqueuePrefetch(pi_queue Queue, const void *Ptr, size_t Size,
   // Lock automatically releases when this goes out of scope.
   std::lock_guard<std::mutex> lock(Queue->PiQueueMutex);
 
-  _pi_ze_event_list_t TmpWaitList;
-  if (auto Res = TmpWaitList.createAndRetainPiZeEventList(NumEventsInWaitList,
-                                                          EventWaitList, Queue))
-    return Res;
-
   // Get a new command list to be used on this call
   pi_command_list_ptr_t CommandList{};
   // TODO: Change UseCopyEngine argument to 'true' once L0 backend