settings.yml clean up : remove locale

locale was declared for bing* engines and vimeo.

  * bing* engines use the language settings.
  * vimeo uses neither locale nor language settings.

This avoid confusion

searx/settings.yml

 
   - name : bing
     engine : bing
-    locale : en-US
     shortcut : bi
 
   - name : bing images
     engine : bing_images
-    locale : en-US
     shortcut : bii
 
   - name : bing news
     engine : bing_news
-    locale : en-US
     shortcut : bin
 
   - name : btdigg
 
   - name : vimeo
     engine : vimeo
-    locale : en-US
     shortcut : vm
 
 #The blekko technology and team have joined IBM Watson! -> https://blekko.com/