Can't upload group avatar

This bug happens on GitLab.com

Summary

When choosing an image to upload as a group avatar, the group-edit page never shows the image filename so pressing save does nothing.

I tried this on 8.15.1 and 8.15.4 and the problem does not manifest on those versions of GitLab

Steps to reproduce

1. Go to edit the settings on a group, example: https://gitlab.com/groups/dewet-test-group/edit
2. Choose a picture to upload and change the group avatar

Expected behavior

The text File name... to the right of Choose File should change to the name of the file.

Actual behavior

It still says File name... as if no file was ever chosen for upload.

Ping @jschatz1