Update rest-api-spec

Author: pquentin

output/openapi/elasticsearch-openapi.json

@@ -28,9 +28,9 @@
       ]
     },
     "params": {
-      "flat_settings": {
+      "include_remotes": {
         "type": "boolean",
-        "description": "Return settings in flat format (default: false)"
+        "description": "Include remote cluster data into the response (default: false)"
       },
       "timeout": {
         "type": "time",