Revert "Move get_user_count_txn out of base store"

This reverts commit 00f0d67566.

Its going to get removed soon, so lets not make merge conflicts.

synapse/storage/_base.py

@@ -1440,6 +1440,18 @@ class SQLBaseStore(object):
 
         return cls.cursor_to_dict(txn)
 
+    def get_user_count_txn(self, txn):
+        """Get a total number of registered users in the users list.
+
+        Args:
+            txn : Transaction object
+        Returns:
+            int : number of users
+        """
+        sql_count = "SELECT COUNT(*) FROM users WHERE is_guest = 0;"
+        txn.execute(sql_count)
+        return txn.fetchone()[0]
+
     def _simple_search_list(
         self, table, term, col, retcols, desc="_simple_search_list"
     ):

synapse/storage/data_stores/main/__init__.py

@@ -516,18 +516,6 @@ class DataStore(
         retval = {"users": users, "total": count}
         return retval
 
-    def get_user_count_txn(self, txn):
-        """Get a total number of registered users in the users list.
-
-        Args:
-            txn : Transaction object
-        Returns:
-            int : number of users
-        """
-        sql_count = "SELECT COUNT(*) FROM users WHERE is_guest = 0;"
-        txn.execute(sql_count)
-        return txn.fetchone()[0]
-
     def search_users(self, term):
         """Function to search users list for one or more users with
         the matched term.