Resolve "Commits and Merge Requests does not list all files when one file exceeds size limits"

What does this MR do?

We used to force expanded: true as an option when getting a merge request diff, but in practice the diffs were always truncated given the behavior of Gitlab::Git::Diff of always truncating patches greater than 100.kilobytes. The Gitaly path respects the expanded option, so to keep the old behavior we stop forcing expanded: true.

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides

Closes #49907 (moved)