Remove root user 100 project limit

What does this MR do?

• Remove root user 100 project limit
• The application default is 100,000

Are there points in the code the reviewer needs to double check?

To update your existing root user,

$ bundle exec rails c
> User.find_by(username: 'root').update(projects_limit: 100000)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Closes #43271 (closed)