No way to clear uploaded avatar from profile

Summary

Gitlab native user avatars are blocking the usage of Gravatars because Gitlab avatars have no "Remove/Clear" button (only a way to pick a replacement file).

Steps to reproduce

1. Login as a new user
2. Go to Profile Settings
3. Upload an avatar directly to Gitlab
4. Reconfigure Gitlab (gitlab.rb) to point to a Gravatar server. User's gravatar is never seen. User cannot remove Gitlab-centric avatar to, in theory, allow Gravatar to be seen.

Expected behavior

Expect to see an avatar from a Gravatar server. Non-removable Gitlab-centric avatar is taking precedence.

Results of GitLab Environment Info

8.10.1 Omnibus