[mod] disable qwant & swisscows by default to improve result quality

searx/settings.yml

     engine : qwant
     shortcut : qw
     categories : general
+    disabled : True
 
   - name : qwant images
     engine : qwant
   - name : swisscows
     engine : swisscows
     shortcut : sw
+    disabled : True
 
   - name : twitter
     engine : twitter