Merge Request page has its wider content area on mobile

Summary

Merge Request page has its wider width in the main content area when you're on mobile (typically less than ~ 768px viewport).

Steps to reproduce

1. Have access to https://gitlab.exaple.com/namespace/project/merge_requests/1 where gitlab.exaple.com is your gitlab instance domain.
2. Scroll right in the main context area to see extra blank on right.

• Example Project: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1

What is the current bug behavior?

The main context area is scrollable to right and has extra blank on right.

What is the expected correct behavior?

The main context area should not be scrollable to right.

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com.

Possible fixes

Fix CSS.

Links

• #34468 (closed) (!12528 (merged))