Merge branch 'AbuseReports-should-use-prettier-window-gl-assignment' into 'master'

Update abuse_reports.js.es6 with prettier `window.gl` assignment

## What does this MR do?

Update abuse_reports.js.es6 with prettier `window.gl` assignment provided by @selfup

**Very small change** but marks the beginning of some frontend guidelines I will soon create.

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

## Why was this MR needed?

## What are the relevant issue numbers?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] 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)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5977

app/assets/javascripts/abuse_reports.js.es6

-window.gl = window.gl || {};
 ((global) => {
   const MAX_MESSAGE_LENGTH = 500;
   const MESSAGE_CELL_SELECTOR = '.abuse-reports .message';
@@ -36,4 +35,4 @@ window.gl = window.gl || {};
   }
 
   global.AbuseReports = AbuseReports;
-})(window.gl);
+})(window.gl || (window.gl = {}));