Revert Yarn workspace changes from #6056 for now.

Yarn currently fails to add the correct symlinks in some cases. See https://github.com/yarnpkg/yarn/issues/4289

package.json

@@ -70,8 +70,5 @@
       "eslint --format=codeframe --fix --rulesdir='./eslint_rules'",
       "git add"
     ]
-  },
-  "workspaces": [
-    "packages/*"
-  ]
+  }
 }