Revert "feat: Add support for returning thread counts for all topics in a course [BD-38] [TNL-8724] [BB-4927] (#29062)" (#29087)

This reverts commit a2f04fb78b.

lms/djangoapps/discussion/rest_api/tests/utils.py

@@ -85,17 +85,6 @@ class CommentsServiceMockMixin:
             status=200
         )
 
-    def register_get_course_commentable_counts_response(self, course_id, thread_counts):
-        """Register a mock response for GET on the CS thread list endpoint"""
-        assert httpretty.is_enabled(), 'httpretty must be enabled to mock calls.'
-
-        httpretty.register_uri(
-            httpretty.GET,
-            f"http://localhost:4567/api/v1/commentables/{course_id}/counts",
-            body=json.dumps(thread_counts),
-            status=200
-        )
-
     def register_get_threads_search_response(self, threads, rewrite, num_pages=1):
         """Register a mock response for GET on the CS thread search endpoint"""
         assert httpretty.is_enabled(), 'httpretty must be enabled to mock calls.'