Move EE code out of AbstractReferenceFilter

This moves EE specific code out of
Banzai::Filter::AbstractReferenceFilter.

ee/lib/ee/banzai/filter/abstract_reference_filter.rb

+# frozen_string_literal: true
+
+module EE
+  module Banzai
+    module Filter
+      module AbstractReferenceFilter
+        extend ::Gitlab::Utils::Override
+
+        override :current_project_namespace_path
+        def current_project_namespace_path
+          @current_project_namespace_path ||= (project&.namespace || group)&.full_path
+        end
+      end
+    end
+  end
+end

lib/banzai/filter/abstract_reference_filter.rb

@@ -327,7 +327,7 @@ module Banzai
       end
 
       def current_project_namespace_path
-        @current_project_namespace_path ||= (project&.namespace || group)&.full_path
+        @current_project_namespace_path ||= project&.namespace&.full_path
       end
 
       private
@@ -359,3 +359,5 @@ module Banzai
     end
   end
 end
+
+Banzai::Filter::AbstractReferenceFilter.prepend(EE::Banzai::Filter::AbstractReferenceFilter)