Remove duplication and update instance saml test

qa/qa/specs/features/browser_ui/1_manage/ee_group/group_saml_sso_spec.rb

@@ -23,7 +23,7 @@ module QA
 
         EE::Page::Group::SamlSSOSignIn.act { click_signin }
 
-        Vendor::SAMLIdp::Page::Login.act { login } if page.has_text?('Enter your username and password')
+        Vendor::SAMLIdp::Page::Login.act { login_if_required }
 
         expect(page).to have_content("Signed in with SAML for #{Runtime::Env.sandbox_name}")
 
@@ -47,7 +47,7 @@ module QA
           click_test_button
         end
 
-        Vendor::SAMLIdp::Page::Login.act { login } if page.has_text?('Enter your username and password')
+        Vendor::SAMLIdp::Page::Login.act { login_if_required }
 
         expect(page).to have_content("Test SAML SSO")
       end

qa/qa/specs/features/browser_ui/1_manage/login/login_via_instance_wide_saml_sso_spec.rb

@@ -8,7 +8,7 @@ module QA
 
         Page::Main::Login.act { sign_in_with_saml }
 
-        Vendor::SAMLIdp::Page::Login.act { login }
+        Vendor::SAMLIdp::Page::Login.act { login_if_required }
 
         expect(page).to have_content('Welcome to GitLab')
       end

qa/qa/vendor/saml_idp/page/login.rb

@@ -7,7 +7,8 @@ module QA
     module SAMLIdp
       module Page
         class Login < Page::Base
-          def login
+          def login_if_required
+            if page.has_text?('Enter your username and password')
               fill_in 'username', with: 'user1'
               fill_in 'password', with: 'user1pass'
               click_on 'Login'
@@ -16,4 +17,5 @@ module QA
         end
       end
     end
+  end
 end