Updated test:unit script for Comments-UI

refs https://github.com/TryGhost/Toolbox/issues/400

- this package won't pass tests on Node 16 because of the use of
  `fetch`, but that's ok because we publish using Node 18 anyway
- this switches the test command to just ensuring the package can build

apps/comments-ui/package.json

@@ -21,7 +21,7 @@
     "preview": "vite preview",
     "test": "vitest run",
     "test:ci": "yarn test --coverage",
-    "test:unit": "yarn test:ci",
+    "test:unit": "yarn build",
     "lint": "eslint src --ext .js --cache",
     "preship": "yarn lint",
     "ship": "STATUS=$(git status --porcelain); echo $STATUS; if [ -z \"$STATUS\" ]; then yarn version; fi",