Removed sync argument (#348)

Author: martin-neotech

neo4j/work/simple.py

@@ -107,7 +107,7 @@ def _connect(self, access_mode):
             self._disconnect()
         self._connection = self._pool.acquire(access_mode, timeout=self._config.acquire_timeout)
 
-    def _disconnect(self, sync=None):  # TODO: remove sync arg
+    def _disconnect(self):
         if self._connection:
             self._connection.in_use = False
             self._connection = None