[REST-API] fix url for reload_secure_settings

rest-api-spec/src/main/resources/rest-api-spec/api/nodes.reload_secure_settings.json

@@ -1,6 +1,6 @@
 {
   "nodes.reload_secure_settings": {
-    "documentation": "http://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-nodes-reload-secure-settings.html",
+    "documentation": "https://www.elastic.co/guide/en/elasticsearch/reference/master/secure-settings.html#reloadable-secure-settings",
     "methods": ["POST"],
     "url": {
       "path": "/_nodes/reload_secure_settings",