Fix fetching linked file for added and removed files

What does this MR do and why?

This MR fixes fetching added and removed linked files. Previously if you copied a link to an added or removed diff file you would get an error.

Screenshots or screen recordings

Before After
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How to set up and validate locally

  1. Open any merge request with added or removed text file
  2. Copy a link to a line in this file on the 'Changes' tab
  3. Open that link in a new tab
  4. Observe that linked file loads without any issues

Merge request reports

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