Throttle the update of `project.pushes_since_gc` to 1 minute

What does this MR do?

Throttle the update of project.pushes_since_gc to alleviate DB load

What are the relevant issue numbers?

Relates to #15094 (closed)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• [ ] Documentation created/updated
• [ ] API support added
• Tests
  • [ ] Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together