Geo: Disable backoff for file attachment types

What does this MR do?

This MR fixes the GitLab Geo attachment replication user uploads attachment to the primary node QA test which is failing.

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/7904

Does this MR meet the acceptance criteria?

• [ ] Changelog entry added, if necessary
• [ ] Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• [ ] Conforms to the database guides
• EE specific content should be in the top level /ee folder
• ~[ ] For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?~~