Fix awardable button mutuality loading spinners

## What does this MR do?
Removes the showing and hiding of loading spinners when an awardable's opposite button is selected. 

## Are there points in the code the reviewer needs to double check?
Shouldn't be

## Why was this MR needed?
Makes the UI more consistent. Reduces confusion of why another button is showing the loading spinner when it was not clicked on.

## What are the relevant issue numbers?
Closes #18380 

## Screenshots (if relevant)
Before:
![loading](/uploads/d4c4e565fa58fbbf3db6ed8e28f9abb0/loading.gif)

After:
![CcwRYZcUVm](/uploads/b93fd04853f43a6c70de3cefb20d08a1/CcwRYZcUVm.gif)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [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 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 !5745