Replace :matrix.org with :example.com

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

roles/custom/matrix-bridge-appservice-slack/defaults/main.yml

@@ -141,7 +141,7 @@ matrix_appservice_slack_configuration_extension_yaml: |
     # Optional
     #slack_master_token: "abc-123-def"
     # Optional
-    #matrix_admin_room: "!aBcDeF:matrix.org"
+    #matrix_admin_room: "!aBcDeF:example.com"
     #homeserver:
     #    url: http://localhost:{{ matrix_synapse_container_client_api_port }}
     #    server_name: my.server