Fix the unstable Github Action

[kyle-sammons]

Summary

We've been having our Github Action that tags latest with unstable failing, despite using the API as the documentation describes. It looks like according to this bug report, the issue is a bug in the underlying REST library and can be worked around by not passing in the tag as refs/tags/{tag}, but instead as tags/{tag}

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.