Consider clearing Redis cache after every spec

The following discussion from !96320 (merged) should be addressed:

• @stanhu started a discussion: (+1 comment)

  @vyaklushin @rymai I wonder if we should just make clean_gitlab_redis_cache the default now that ProtectedBranches::CacheService uses Gitlab::Redis::Cache directly--or somehow automatically detect Redis caching is used and then trigger this.

This has caused 2 broken masters: !96320 (merged) and !96111 (merged)