chore(deps): bump @tiptap/extension-placeholder

Bumps [@tiptap/extension-placeholder](https://github.com/ueberdosis/tiptap/tree/HEAD/packages/extension-placeholder) from 2.4.0 to 2.5.1.
- [Release notes](https://github.com/ueberdosis/tiptap/releases)
- [Changelog](https://github.com/ueberdosis/tiptap/blob/develop/packages/extension-placeholder/CHANGELOG.md)
- [Commits](https://github.com/ueberdosis/tiptap/commits/@tiptap/extension-placeholder@2.5.1/packages/extension-placeholder)

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

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