Fix parallel diff expansion line numbers

What does this MR do?

For the diff expansion part of #205938 (closed), which only happens on collapsed diffs in the middle of the file in parallel view.

The diff expansion cell component expects the inline lines to be present regardless of which view type is being used. This MR updates the logic to check the appropriate diff type.

Context

This regression was originally caused by !19930 (merged) (merged over 1 month ago), but wasn't exposed until testing the feature across all of GitLab (#197897 (comment 288703756)).

Screenshots

Before	After

Does this MR meet the acceptance criteria?

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