[fix] enable bing by default / was disabled in cea7b71d14

The engine was deactivated at that time (in #1235) because there were problems,
but they are fixed now.

[PR 1235] https://github.com/searxng/searxng/pull/1235

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/settings.yml

@@ -384,7 +384,6 @@ engines:
   - name: bing
     engine: bing
     shortcut: bi
-    disabled: true
 
   - name: bing images
     engine: bing_images