update move-to-step spec with proper docs and extra warning to clients (#35477)

x-pack/plugin/src/test/resources/rest-api-spec/api/ilm.move_to_step.json

@@ -1,6 +1,7 @@
 {
   "ilm.move_to_step": {
-    "documentation": "http://www.elastic.co/guide/en/index_lifecycle/current/index_lifecycle.html",
+    "documentation": "https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-move-to-step.html",
+    "description": "Triggers execution of a specific step in the lifecycle policy. Since this action is designed to only be run in emergency situations, clients should not implement this API",
     "methods": [ "POST" ],
     "url": {
       "path": "/_ilm/move/{index}",