Bump tinymce from 6.8.4 to 7.2.0 in /app-engine/frontend (#232)

Bumps [tinymce](https://github.com/tinymce/tinymce/tree/HEAD/modules/tinymce) from 6.8.4 to 7.2.0.
- [Changelog](https://github.com/tinymce/tinymce/blob/main/modules/tinymce/CHANGELOG.md)
- [Commits](https://github.com/tinymce/tinymce/commits/7.2.0/modules/tinymce)

---
updated-dependencies:
- dependency-name: tinymce
  dependency-version: 7.2.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

app-engine/frontend/package.json

@@ -83,7 +83,7 @@
     "react-router": "5.3.4",
     "react-router-dom": "5.3.4",
     "redux": "4.2.1",
-    "tinymce": "6.8.4",
+    "tinymce": "7.2.0",
     "xss": "1.0.15"
   }
 }