Fix bug where changelog is always slightly out of date on release tags

[wren]

As the title says, there's currently a bug in our release process where the release is tagged and published, and then the changelog is updated afterward. You can actually see it if you go through the tags in our repo and click on the changelog file for each one.

This PR makes it a part of the changelog step in CI to update the tag to the proper commit after the changelog is generated (the changelog generator itself requires a tag to work, which is why the tag has to be moved afterward instead of beforehand).

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.

[micahellison]

🏷