Commit diff header box has zero inner padding

Problem

In the header block for the the 'Changes' tab when looking at the diff for a commit, the text and navigation buttons are touching the background marging

You can check the image below:

From : omnibus-gitlab@56ce0d27

This behavior contrasts to how it is implemented in the MR 'Changes' tab which the background overflows to the edges:

Proposal

We should either make the background overflows and touch the navigation bar edges or create an inner padding to align with the file names below it.