Merge Request Diff has an extra spacing on mobile

Summary

Merge Request Diff has an extra spacing on side on mobile.

Steps to reproduce

Access to !42821 (diffs) on mobile.

What is the current bug behavior?

What is the expected correct behavior?

Relevant logs and/or screenshots

See above.

Output of checks

This bug happens on GitLab.com (EE 13.4-pre).

Possible fixes