WIP: Bug: Allow upload of *.gitlab-license

What does this MR do?

Fixes bug where **.gitlab-license files cannot be uploaded. Possibly due to a rails5 upgrade issue?

WIP I don't love this fix and I cannot figure out where the dot-prefix is coming from, but this does fix the regression. Happy to follow-up with some suggestions on a better approach if anyone has insight into how ActionDispatch should be parsing this to a proper file.

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/9035

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• 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?
• Security reports checked/validated by reviewer