Fix code block a bit

Related to #549 (Github Pull Request)

docs/configuring-playbook-ma1sd.md

@@ -76,7 +76,8 @@ To learn more about how to do this, refer to the information about `matrix_ma1sd
 
 If your use case requires mobile verification, it is quite simple to integrate ma1sd with [Twilio](https://www.twilio.com/), an online telephony services gateway. Their prices are reasonable for low-volume projects and integration can be done with the following configuration:
 
-```matrix_ma1sd_configuration_extension_yaml: |
+```yaml
+matrix_ma1sd_configuration_extension_yaml: |
   threepid:
     medium:
       msisdn: