Removes site search from all-content finder
Removes site search from all-content finder

We are starting to work on the generic finder and therefore it will eventually
replace site search. This commit removes the site search field in the header
for all-content finder. Finders already have a "search" field and it seems weird to have two
search fields on the page doing different things and returning different
results.

Eventually all finders will only have one search find.

alphagov/finder-frontend,alphagov/finder-frontend,alphagov/finder-frontend,alphagov/finder-frontend