Change default user id to mirror official docs

roles/matrix-cactus-comments/defaults/main.yml

@@ -17,7 +17,7 @@ matrix_cactus_comments_app_service_env_file: "{{ matrix_cactus_comments_base_pat
 matrix_cactus_comments_as_token: ''
 matrix_cactus_comments_hs_token: ''
 matrix_cactus_comments_homeserver_url: ''
-matrix_cactus_comments_user_id: cactus-comments
+matrix_cactus_comments_user_id: "cactusbot"
 
 matrix_cactus_comments_container_port: 5000