[fix-2146] set different HTTP Referer header to DuckDuckGo requests

For what ever reasons, ddg-lite don't like the Referer

  https://lite.duckduckgo.com/

In an interactive session in the WEB browser the the Reverer has exactly this
value, but ddg-lite don't like this value when the request is build up by
SearXNG.  The new value is:

  https://google.com/

What fakes a user comes from a google link.

Related: https://github.com/searxng/searxng/pull/2081
Closes: https://github.com/searxng/searxng/issues/2146



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