Fix spelling errors

-------8<-------
SUMMARY:
unsupport     1

prometheus_xmpp/__main__.py

@@ -411,7 +411,7 @@ def password_cb():
         config['alertmanager_url'] = env['ALERTMANAGER_URL']
 
     if config.get('format') not in ('full', 'short', None):
-        parser.error("unsupport config format: %s" % config['format'])
+        parser.error("unsupported config format: %s" % config['format'])
 
     return (
         jid,