Pull request line numbers run together in files with 10K+ lines (BB-15811)

While reviewing a pull request [1] I noticed that in the third hunk, where the line numbers jump above 10K, that the line numbers on the old and new versions run together making it kind of hard to read.

[1] https://bitbucket.org/pidgin/main/pull-requests/19/luminanosity-contrast-check/diff