api: Fix edit-message example.
The message ID necessarily has to be an integer, and if no casting is
made it was being considered a string, causing problems when running
the example.
@@ -36,7 +36,7 @@ Specify your Zulip API credentials and server in a ~/.zuliprc file or using the
import zulip
parser = zulip.add_default_arguments(argparse.ArgumentParser(usage=usage))
-parser.add_argument('--message-id', default="")
+parser.add_argument('--message-id', type=int)
parser.add_argument('--subject', default="")
parser.add_argument('--content', default="")
options = parser.parse_args()
