Support common table expressions

Fixes ActiveRecord::WithTest#test_common_table_expressions_are_unsupported

Author: aidanharan

lib/active_record/connection_adapters/sqlserver_adapter.rb

@@ -188,6 +188,10 @@ def supports_optimizer_hints?
         true
       end
 
+      def supports_common_table_expressions?
+        true
+      end
+
       def supports_lazy_transactions?
         true
       end