Remove client param for external search

[remusao]

Firefox sends client info with every search to Google (maybe other search engines)? Should we do something about that? browser/components/search/extensions/google/_locales/en/messages.json https://github.com/cliqz-oss/browser-f/blob/master/mozilla-release/browser/components/search/extensions/google/_locales/en/messages.json#L12

[chrmod]

It's unlike we will have Search deal with Google :-) Not sure when or even if it is worth to change it.