fix: [opendata export] No longer using the returnFormat field as the dataset resource format

- The resource format can be defined with a
  'format' field within the resource field in the
  setup filter

app/Lib/Export/OpendataExport.php

@@ -71,6 +71,7 @@ class OpendataExport
 
     private function __add_query($cmd)
     {
+        unset($this->__default_filters['returnFormat']);
         $body = json_encode($this->__default_filters);
         $bodyFilename = $this->__generateSetupFile($body);
         $bodyParam = ' --body ' . $bodyFilename;