You probably won't need to do this often (if ever at all) but just in case, here is how to delete a tag from a remote Git repository.
If you have a tag named '12345' then you would just do this:
git tag -d 12345 git push origin :refs/tags/12345
That will remove '12345' from the remote repository.
If I just made your day a little better then thank me with a coffee: