Add support for activerecord 6.1.4 using a cherry picked patch

Forwarded: https://github.com/kmurph73/ctes_in_my_pg/commit/eabb5508df56b5dc838547655542a272511af424

--- a/config/initializers/postgresql_cte.rb
+++ b/config/initializers/postgresql_cte.rb
@@ -96,7 +96,7 @@
       end
     end
 
-    def build_arel(aliases)
+    def build_arel(aliases = nil)
       arel = super
 
       build_with(arel) if @values[:with]