Clean up globals exemptions within .eslintrc

## What does this MR do?

Removes unnecessarily-exempted globals from `.eslintrc` where possible.

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

`npm run eslint` should return 0 errors.

## Why was this MR needed?

see Issue #24756 

## Does this MR meet the acceptance criteria?

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

## What are the relevant issue numbers?

Closes #24756

See merge request !7642