Merge branch 'pavelloz/gitlab-ce-18731-form-actions-leaking' into 'master'

Prevent .form-actions from leaking out of the container (originally by @pavelloz)

{+addition+} **This MR was originally by @pavelloz in !4889, the MR was inactive for 2 months and is a ~P3, I have credited @pavelloz in the `CHANGELOG`. The description below is also copied from that MR.**

## What does this MR do?
Fixes div width leaking outside  

## Are there points in the code the reviewer needs to double check?
Any place where it might been needed when introduced couple months ago.

## Why was this MR needed?

## What are the relevant issue numbers?
{+addition+}
Closes #18731.
## Screenshots (if relevant)
Before
![image](/uploads/f7bfb18a5949e95ab876f8c140ef1c91/image.png)
![image](/uploads/81d4f99ba3334f46f04bd078eefa2548/image.png)


After
![image](/uploads/f34b1e2bf4d8849275c206e66ccb8398/image.png)
![image](/uploads/2664adfcf00ca6831629a8fdab68f6f6/image.png)


## Does this MR meet the acceptance criteria?

- [x] [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
  - [x] Added for this feature/bug
  - [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)

cc @jschatz1

See merge request !6075

CHANGELOG

@@ -26,6 +26,7 @@ v 8.12.0 (unreleased)
   - Update merge_requests.md with a simpler way to check out a merge request. !5944
   - Fix button missing type (ClemMakesApps)
   - Move to project dropdown with infinite scroll for better performance
+  - Fix leaking of submit buttons outside the width of a main container !18731 (originally by @pavelloz)
   - Load branches asynchronously in Cherry Pick and Revert dialogs.
   - Add merge request versions !5467
   - Change using size to use count and caching it for number of group members. !5935

app/assets/stylesheets/framework/forms.scss

@@ -19,7 +19,6 @@ input[type='text'].danger {
 }
 
 .form-actions {
-  margin: -$gl-padding;
   margin-top: 0;
   margin-bottom: -$gl-padding;
   padding: $gl-padding;