Merge branch 'remove-unused-indexes' into 'master'

Remove various redundant indexes

## What does this MR do?

This MR removes various redundant and unused indexes. See c3d5c536d9c77dbe183744cb19f2cdab7ee606fd for more information.

## Are there points in the code the reviewer needs to double check?

No.

## Why was this MR needed?

Unused indexes are a waste of storage space and slow down database writes. If they are ever needed again we can re-create them. There's no point in hoarding indexes because you _may_ need them in the future.

## What are the relevant issue numbers?

#20767

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5759

1 files changed, 1 insertions, 0 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 80ad5f37f17..e144bae24bc 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -28,6 +28,7 @@ v 8.11.0 (unreleased)
   - Add experimental Redis Sentinel support !1877
   - Fix branches page dropdown sort initial state (ClemMakesApps)
   - Environments have an url to link to
+  - Various redundant database indexes have been removed
   - Update `timeago` plugin to use multiple string/locale settings
   - Remove unused images (ClemMakesApps)
   - Limit git rev-list output count to one in forced push check