Disable page numbers for all project dashboards

What does this MR do?

This disables page numbers for Dashboard::ProjectsController#index and Dashboard::ProjectsController#starred. This ensures these pages use the same pagination system as Explore::ProjectsController and that these pages don't spend time running expensive COUNT queries.

Screenshots

Before:

After:

First page:

Second page:

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Review
  • Has been reviewed by UX
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/27376

cc @sarrahvesselov