It turns out we can't work with version 1.1 of guzzle6-adapter (because it do...

It turns out we can't work with version 1.1 of guzzle6-adapter (because it does not implement PSR client interface). We should revert this but to the stable version (^2.0). Geocoder has fixed the issue #3160832: Support for v2.0 of php-http/guzzle6-adapter and we don't need to do this anymore.