Change language opt-out to language opt-in (#7823)

* Switch filtered_languages to chosen_languages

* Adjust interface

* Remove unused translations

spec/models/user_spec.rb

@@ -41,9 +41,9 @@ RSpec.describe User, type: :model do
     end
 
     it 'cleans out empty string from languages' do
-      user = Fabricate.build(:user, filtered_languages: [''])
+      user = Fabricate.build(:user, chosen_languages: [''])
       user.valid?
-      expect(user.filtered_languages).to eq []
+      expect(user.chosen_languages).to eq nil
     end
   end