Follow up to T255305: [Investigation] - Consider if the Wikibase cache for CachingEntityRevisionLookup is needed any more.

RevisionLookup::getKnownCurrentRevision() has a much better caching system than PrefetchingWikiPageEntityMetaDataAccessor which is a simple LRU cache that gets reset in every request.
This is doubly important since we are dropping CachingEntityRevisionLookup in T260600 which means caching will be based on revision id and not the page title (increasing revision id lookup: T255305#6380897) Making the drop slightly more like a ticking bomb.