fix(deploy): drop invalid stop_reason key (blocked automation reload) [#734]

stop action takes the message inline; stop_reason is not in the 2026.8
script schema and validation failure aborts the whole automations reload.
Detail: https://projects.knownelement.com/issues/734

automations.yaml

@@ -250,8 +250,7 @@
     - condition: template
       value_template: "{{ trigger.json.ref | default('') != 'refs/heads/master' }}"
     then:
-    - stop: non-master ref ignored
-      stop_reason: "deploy webhook: non-master ref {{ trigger.json.ref | default('') }}"
+    - stop: "deploy webhook: non-master ref {{ trigger.json.ref | default('') }} ignored"
   - variables:
       changed_files: >-
         {{ (trigger.json.commits | default([]) | map(attribute='added') | flatten | list)