Merge branch '433173_add_idx_on_member_approval_memb_namespace_id_and_status' into 'master'

Added index for member_approval on member_namespace_id and status

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/149044



Merged-by: Michał Zając <mzajac@gitlab.com>
Approved-by: Tarun Vellishetty <tvellishetty@gitlab.com>
Approved-by: Imre Farkas <ifarkas@gitlab.com>
Approved-by: Michał Zając <mzajac@gitlab.com>
Co-authored-by: Suraj Tripathi <stripathi@gitlab.com>