Bump @tiptap/extension-superscript from 2.5.9 to 2.6.6 in /client

Bumps [@tiptap/extension-superscript](https://github.com/ueberdosis/tiptap/tree/HEAD/packages/extension-superscript) from 2.5.9 to 2.6.6.
- [Release notes](https://github.com/ueberdosis/tiptap/releases)
- [Changelog](https://github.com/ueberdosis/tiptap/blob/develop/packages/extension-superscript/CHANGELOG.md)
- [Commits](https://github.com/ueberdosis/tiptap/commits/@tiptap/[email protected]/packages/extension-superscript)

---
updated-dependencies:
- dependency-name: "@tiptap/extension-superscript"
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>