Ensure that boolean params in the API are parsed for truthiness (#6575)

Use Rails smart boolean cast to account for values such as "f",
"0", "false", etc. Previously, if a param was present in the request,
it would count as true.

app/controllers/api/v1/accounts/search_controller.rb

@@ -22,8 +22,4 @@ class Api::V1::Accounts::SearchController < Api::BaseController
       following: truthy_param?(:following)
     )
   end
-
-  def truthy_param?(key)
-    params[key] == 'true'
-  end
 end