Use render :json correctly

DEPRECATION WARNING: `render :text` is deprecated because it does not
actually render a `text/plain` response. Switch to `render plain: 'plain
text'` to render as `text/plain`, `render html: '<strong>HTML</strong>'`
to render as `text/html`, or `render body: 'raw'` to match the
deprecated behavior and render with the default Content-Type, which is
`text/html`.

app/controllers/api_controller.rb

@@ -154,7 +154,7 @@ def crawl
         success = sub.feed.crawl
       end
     end
-    render text: {a: (success ? true : false) }.to_json
+    render json: {a: (success ? true : false) }.to_json
     # render_json_status(success ? true : false)
     # return render_json_status(success ? true : false)
   end