Clean up image diff 2-up mode
<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=19576) </details> <!--IssueSummary end--> Follow up after https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14397 is done Would love to have that same layout as in https://github.com/cameronmcefee/Image-Diff-View-Modes/commit/8e95f70c9c47168305970e91021072673d7cdad8: - images one 1 line - smaller image centered both ways within the invisible bounding box the image would have had, if it was just as big - size attributes be colored red and green respectively (think this is pretty nice) - place the images always horizontal from each other, regardless of inline/side-by-side ![image](/uploads/df0b581e4f6ea9987b84f8b1d5f3f3d0/image.png) cc: @ClemMakesApps
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