Remove defaultAuthors from MR Analytics and VSA

What does this MR do and why?

This MR remove the unnecessary defaultAuthors attribute from the MR analytics and VSA filter bars. The AuthorToken handles this functionality natively for the requirements of these features.

Screenshots or screen recordings

n/a

How to set up and validate locally

• Browse to MR Analytics or VSA and play around with the filters
  • http://localhost:3001/gitlab-org/gitlab-shell/-/analytics/merge_request_analytics
  • http://localhost:3001/gitlab-org/gitlab-shell/-/value_stream_analytics

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #342241 (closed)