Remove extra period in is_mongos documentation (#967)

Author: atiabbz

pymongo/mongo_client.py

@@ -1080,7 +1080,7 @@ def is_primary(self) -> bool:
     def is_mongos(self) -> bool:
         """If this client is connected to mongos. If the client is not
         connected, this will block until a connection is established or raise
-        ServerSelectionTimeoutError if no server is available..
+        ServerSelectionTimeoutError if no server is available.
         """
         return self._server_property("server_type") == SERVER_TYPE.Mongos