Clear changes to settings after checking form saves them (#15746)

* Clear the cached community name before loading new page

When the creator settings form had been run before the create new page
spec, the community name would be changed from the default
"DEV(local)" to "Climbing Life". Since the application helper can
memoize this value - and the database will not - ensure these are in
sync by clearing the settings cache before requesting the page (which
will be prefilled based on the setting).

This "fix" should probably be moved into the test introducing the
change, rather than the one impacted by it.

* Move clearing the settings cache closer to the change

Rather than clearing the cache where we were impacted, clear
immediately after the save spec completes.

spec/forms/creator_settings_form_spec.rb

@@ -34,6 +34,13 @@ RSpec.describe CreatorSettingsForm, type: :model do
   describe "#save" do
     let(:current_user) { create(:user) }
 
+    after do
+      # prevent changes here from leaking into other tests
+      Settings::Community.clear_cache
+      Settings::UserExperience.clear_cache
+      Settings::Authentication.clear_cache
+    end
+
     # rubocop:disable RSpec/ExampleLength
     it "saves the updated attributes to the correct Settings values", :aggregate_failures do
       # NOTE: override the profile migration hack from rails_helper.rb