[fix] google engine: don't overspecify the search query to Google

The method EngineTraits.get_region(..) returns engine's region string
that **best fits** to SearXNG's locale.  This means it returns a
region (country) if only a language is set in the locale.  By example the method
returns for a locale tag `es` a region `ES`.

Google's search parameter `cr` restricts search results to documents originating
in a particular country / in case of a locale tag (language) as described above,
this argument should be unset in the query send to Google.

Closes: https://github.com/searxng/searxng/issues/2672


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