Disable invisible_captcha feature flag

ee/spec/controllers/registrations_controller_spec.rb

 require 'spec_helper'
 
 describe RegistrationsController do
+  before do
+    stub_feature_flags(invisible_captcha: false)
+  end
+
   describe '#create' do
     context 'when the user opted-in' do
       let(:user_params) { { user: attributes_for(:user, email_opted_in: '1') } }

ee/spec/features/signup_spec.rb

@@ -3,6 +3,10 @@ require 'spec_helper'
 describe 'Signup on EE' do
   let(:user_attrs) { attributes_for(:user) }
 
+  before do
+    stub_feature_flags(invisible_captcha: false)
+  end
+
   context 'for Gitlab.com' do
     before do
       expect(Gitlab).to receive(:com?).and_return(true).at_least(:once)