mem-ruby: bug fix for Finish_CopyBack_Stale

I made a mistake in the change below:
https://gem5-review.googlesource.com/c/public/gem5/+/58413

Checking the requestor in the sharer list for eviction
should be removed now. If the sharer count is zero, the requestor can't
be in the sharer list.

Change-Id: I304d2dd7df1aff4907801664a260c35c490a2136
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/62991
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>

src/mem/ruby/protocol/chi/CHI-cache-actions.sm

@@ -900,7 +900,7 @@ action(Finish_CopyBack_Stale, desc="") {
   // if it was the last known sharer and we don't have the data do the same
   // the Initiate_Evict
   if ((is_HN == false) && (tbe.dir_sharers.count() == 0) &&
-      tbe.dir_sharers.isElement(tbe.requestor) && (tbe.dataValid == false)) {
+      (tbe.dataValid == false)) {
     tbe.actions.push(Event:SendEvict);
   }
 }