Fix crash when checking external authorization

Only check the global feature directly on `License` otherwise we would
also perform the check on the namespace which would cause a crash.

ee/app/models/ee/project.rb

@@ -489,7 +489,7 @@ module EE
     end
 
     def external_authorization_classification_label
-      return nil unless feature_available?(:external_authorization_service)
+      return nil unless License.feature_available?(:external_authorization_service)
 
       super || ::Gitlab::CurrentSettings.current_application_settings
                  .external_authorization_service_default_label

ee/spec/models/project_spec.rb

@@ -1292,6 +1292,14 @@ describe Project do
       expect(project.external_authorization_classification_label)
         .to eq('hello')
     end
+
+    it 'does not break when not stubbing the license check' do
+      enable_external_authorization_service
+      enable_namespace_license_check!
+      project = build(:project)
+
+      expect { project.external_authorization_classification_label }.not_to raise_error
+    end
   end
 
   describe '#user_can_push_to_empty_repo?' do

ee/spec/support/ee/license_helpers.rb

@@ -7,7 +7,7 @@ module EE
     #   stub_licensed_features(geo: true, deploy_board: false)
     #
     # This enables `geo` and disables `deploy_board` features for a spec.
-    # Other features are still enabled/disabled as defined in the licence.
+    # Other features are still enabled/disabled as defined in the license.
     def stub_licensed_features(features)
       allow(License).to receive(:feature_available?).and_call_original