Only check index status if modifying Advanced Search form

This change was first introduced in merge request
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/62135.

Changelog: fixed

ee/changelogs/unreleased/321742-elasticsearch-index_exists-check-should-only-happen-when-changi.yml

----
-title: Only check index status if modifying Advanced Search form
-merge_request: 62135
-author:
-type: fixed