Fix broken link in changelog

CHANGELOG.md

@@ -13,7 +13,7 @@ matrix_synapse_rc_message_burst_count: 10.0
 
 The playbook can now install and configure [matrix-synapse-shared-secret-auth](https://github.com/devture/matrix-synapse-shared-secret-auth) for you.
 
-Additional details are available in [Setting up the Shared Secret Auth password provider module](configuring-playbook-shared-secret-auth.md).
+Additional details are available in [Setting up the Shared Secret Auth password provider module](docs/configuring-playbook-shared-secret-auth.md).
 
 
 # 2018-08-17