[Package] Move Gmail to the Recommended list (#138)

According to our new recommendation guidelines (see the FAQ in the wiki), Gmail needs to move from the `Advanced` list to the `Recommended` list:
- The app is available on the Google Play Store
- Removing this app won't break any core feature of the phone nor will it cause data (emails) loss

Package(s):
- com.google.android.gm

resources/assets/uad_lists.json

@@ -17691,7 +17691,7 @@
     "dependencies": null,
     "neededBy": null,
     "labels": null,
-    "removal": "Advanced"
+    "removal": "Recommended"
   },
   {
     "id": "com.google.android.ims",