chore: v4.2.1 (#6362)

## Summary

Bump to v4.2.1

## Related Issues / Discussions

n/a

## QA Instructions

n/a

## Merge Plan

Do the release after merging.

## Checklist

- [x] _The PR has a short but descriptive title, suitable for a
changelog_
- [ ] _Tests added / updated (if applicable)_
- [ ] _Documentation added / updated (if applicable)_

invokeai/version/invokeai_version.py

@@ -1 +1 @@
-__version__ = "4.2.0"
+__version__ = "4.2.1"