Fix strings: Cactus Chat → Cactus Comments

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

docs/configuring-playbook-cactus-comments.md

@@ -21,7 +21,7 @@ Add the following block to your `vars.yaml` and make sure to exchange the tokens
 
 ```yaml
 #################
-## Cactus Chat ##
+## Cactus Comments ##
 #################
 
 # This enables the backend (appservice)