Clean up of RSpec/LetSetup within spec/models (#28444)

spec/models/user_spec.rb

@@ -422,6 +422,7 @@ RSpec.describe User do
 
     it 'deactivates all sessions' do
       expect(user.session_activations.count).to eq 0
+      expect { session_activation.reload }.to raise_error(ActiveRecord::RecordNotFound)
     end
 
     it 'revokes all access tokens' do
@@ -430,6 +431,7 @@ RSpec.describe User do
 
     it 'removes push subscriptions' do
       expect(Web::PushSubscription.where(user: user).or(Web::PushSubscription.where(access_token: access_token)).count).to eq 0
+      expect { web_push_subscription.reload }.to raise_error(ActiveRecord::RecordNotFound)
     end
   end