build(deps): Bump @ibm/plex from 5.2.1 to 6.0.0 in /ui

Bumps [@ibm/plex](https://github.com/ibm/plex) from 5.2.1 to 6.0.0.
- [Release notes](https://github.com/ibm/plex/releases)
- [Changelog](https://github.com/IBM/plex/blob/master/CHANGELOG.md)
- [Commits](IBM/plex@v5.2.1...v6.0.0)

---
updated-dependencies:
- dependency-name: "@ibm/plex"
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

ui/package-lock.json

@@ -81,7 +81,7 @@
   "dependencies": {
     "@carbon/themes": "^10.36.0",
     "@carbon/type": "^10.35.0",
-    "@ibm/plex": "^5.2.1",
+    "@ibm/plex": "^6.0.0",
     "carbon-components": "^10.37.0",
     "carbon-components-react": "^7.43.0",
     "carbon-icons": "^7.0.7",