Fix commented line highlighting

What does this MR do?

Fixes comment highlighting for the new unified diff components. See screenshots.

Screenshots (strongly suggested)

Broken

Notice line 7139 is not highlighted.

Fixed

Notice line 7139 is highlighted.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done