Fix broken `government_search_index` property
Fix broken `government_search_index` property

It should only include `government_edition_classes`, not
everything. Detailed guides have their own method.

Good catch @chrismdp!

hotvulcan/whitehall,robinwhittleton/whitehall,YOTOV-LIMITED/whitehall,ggoral/whitehall,ggoral/whitehall,askl56/whitehall,YOTOV-LIMITED/whitehall,robinwhittleton/whitehall,hotvulcan/whitehall,askl56/whitehall,hotvulcan/whitehall,alphagov/whitehall,hotvulcan/whitehall,alphagov/whitehall,alphagov/whitehall,YOTOV-LIMITED/whitehall,ggoral/whitehall,ggoral/whitehall,robinwhittleton/whitehall,YOTOV-LIMITED/whitehall,askl56/whitehall,robinwhittleton/whitehall,askl56/whitehall,alphagov/whitehall