Fix filter input alignment

## What does this MR do?
If you carefully observe the filter inputs on the [issues page](https://gitlab.com/gitlab-org/gitlab-ce/issues) and the [projects dashboard page](https://gitlab.com/dashboard/projects), you will notice that those input fields are actually a few pixels lower than the UI elements beside them (More so for the projects dashboard page than the issues page). This MR fixes that alignment issue so that they are aligned to the buttons on their right.

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

## Why was this MR needed?
Improves the existing UI

## What are the relevant issue numbers?
Closes #20559 

## Screenshots (if relevant)
Before
![Screen_Shot_2016-08-02_at_5.42.28_PM](/uploads/8530fc6c9ce20f28ae74b950bc1bd6be/Screen_Shot_2016-08-02_at_5.42.28_PM.png)

After
![Screen_Shot_2016-08-02_at_5.49.28_PM](/uploads/ec20e68045c2190aec52e5f059d1a3bc/Screen_Shot_2016-08-02_at_5.49.28_PM.png)

After (with color markings)
![Screen_Shot_2016-08-02_at_5.49.25_PM](/uploads/6e032b1ffb438018f6fadf294c3cebd3/Screen_Shot_2016-08-02_at_5.49.25_PM.png)

Before
![Screen_Shot_2016-08-02_at_5.41.19_PM](/uploads/11a3c30d0290328bb3298bc392facf9f/Screen_Shot_2016-08-02_at_5.41.19_PM.png)

After
![Screen_Shot_2016-08-02_at_5.49.47_PM](/uploads/f8e20346a19dc67cc3e54788dc0e72fb/Screen_Shot_2016-08-02_at_5.49.47_PM.png)

After (with color markings)
![Screen_Shot_2016-08-02_at_5.49.58_PM](/uploads/1839d5681ab2f3518609004511af86a6/Screen_Shot_2016-08-02_at_5.49.58_PM.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 !5633