Quarantine elastic issue search spec

What does this MR do and why?

This MR long-term quarantines ee/spec/models/concerns/search/elastic/issues_search_spec.rb because it was fixed in !157455 (merged), so we can validate in an unquarantine MR.

See incident gitlab-org/quality/engineering-productivity/master-broken-incidents#7050 (closed) and fast-quarantine gitlab-org/quality/engineering-productivity/fast-quarantine!209 (merged)