Remove redundant js-timeago-pending from user activity log

## What does this MR do?
Enables the `skip_js` feature of `time_ago_with_tooltip()` since the frontend was already re-initializing `timeago` on all the elements after it received the data from the backend.

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

## Why was this MR needed?

*  Reduces bandwidth usage (Reduced by ~3.1kb)
*  Removes redundant code
*  Happy DOM 🎈 

## What are the relevant issue numbers?
Closes #21063 

## Screenshots (if relevant)
Before (DOM):
![Screen_Shot_2016-08-18_at_11.14.18_AM](/uploads/8be02cff27e452670988db8ff54bd57c/Screen_Shot_2016-08-18_at_11.14.18_AM.png)

After (DOM):
![Screen_Shot_2016-08-18_at_11.26.51_AM](/uploads/a0c5cbcd4c7b8e524a848b50dbd88c55/Screen_Shot_2016-08-18_at_11.26.51_AM.png)

Before (Bandwidth):
![Screen_Shot_2016-08-18_at_11.28.24_AM](/uploads/c37de0b398d7c66770f1def1777ca11a/Screen_Shot_2016-08-18_at_11.28.24_AM.png)

After (Bandwidth):
![Screen_Shot_2016-08-18_at_11.29.49_AM](/uploads/dc21719b965df1e73c868470447a1b20/Screen_Shot_2016-08-18_at_11.29.49_AM.png)

## 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 !5871