Remove unused var

.buildkite/postgres-config.yaml

 # Configuration file used for testing the 'synapse_port_db' script.
 # Tells the script to connect to the postgresql database that will be available in the
 # CI's Docker setup at the point where this file is considered.
-server_name: "test"
+server_name: "localhost:8080"
 
 signing_key_path: "/src/.buildkite/test.signing.key"
 

.buildkite/sqlite-config.yaml

 # Configuration file used for testing the 'synapse_port_db' script.
 # Tells the 'update_database' script to connect to the test SQLite database to upgrade its
 # schema and run background updates on it.
-server_name: "test"
+server_name: "localhost:8080"
 
 signing_key_path: "/src/.buildkite/test.signing.key"
 

synapse/storage/database.py

@@ -256,8 +256,6 @@ class Database(object):
                 self._check_safe_to_upsert,
             )
 
-        self.rand = random.SystemRandom()
-
     @defer.inlineCallbacks
     def _check_safe_to_upsert(self):
         """