Merge request diff in mobile

Raising this issue because of this one #25930 (closed)

In mobile, the Changes tab in the Merge Request view is not usable. When we have comments, the text overflows, most of the time making it impossible to read.

I am not 100% sure if reviewing a MR in a mobile is a use case, so I am adding UX research label as well.

Side by Side:

Inline:

//cc @awhildy @sarahod