Migrate lastUpdatedAt to lastUpdatedOn

What does this MR do?

In !46549 (merged) we updated the GraphQL API for the codeCoverageSummary to have lastUpdatedOn instead of lastUpdatedAt. This MR migrates the frontend to use that new schema.

This feature is behind a feature flag and it is not user facing so it does not need a changelog.

Screenshots (strongly suggested)

n/a

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