Bump tinymce from 4.5.7 to 5.10.0 in /web-ui

Bumps [tinymce](https://github.com/tinymce/tinymce/tree/HEAD/modules/tinymce) from 4.5.7 to 5.10.0.
- [Release notes](https://github.com/tinymce/tinymce/releases)
- [Changelog](https://github.com/tinymce/tinymce/blob/develop/modules/tinymce/CHANGELOG.md)
- [Commits](https://github.com/tinymce/tinymce/commits/5.10.0/modules/tinymce

)

---
updated-dependencies:
- dependency-name: tinymce
  dependency-type: direct:production
...

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