[erp5_only_office] remote_settings fix schema

bt5/erp5_only_office/SkinTemplateItem/portal_skins/erp5_only_office/onlyoffice/remote_settings.json.json

 {
   "$schema": "http://json-schema.org/draft-07/schema",
   "title": "remote XMLA connections",
+  "type": "object",
   "additionalProperties": {
     "$ref": "xmla_connection.json"
   }
-}
+}
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