fix(endpoints/api): return empty 204 resp

Return an empty body on API requests with status code 204, which
means "No content". Incorrect 'Deleted' responses were being
returned after successful DELETE operations despite the "No Content"
definition of 204.

endpoints/api/user.py

@@ -421,7 +421,7 @@ class User(ApiResource):
       abort(404)
 
     model.user.delete_user(get_authenticated_user(), all_queues)
-    return 'Deleted', 204
+    return '', 204
 
 
 @resource('/v1/user/private')
@@ -873,7 +873,7 @@ class UserAuthorization(ApiResource):
       raise NotFound()
 
     access_token.delete_instance(recursive=True, delete_nullable=True)
-    return 'Deleted', 204
+    return '', 204
 
 @resource('/v1/user/starred')
 class StarredRepositoryList(ApiResource):
@@ -956,7 +956,7 @@ class StarredRepository(RepositoryParamResource):
 
     if repo:
       model.repository.unstar_repository(user, repo)
-      return 'Deleted', 204
+      return '', 204
 
 
 @resource('/v1/users/<username>')