Eliminate remaining use of lease_connection in Arel::TreeManager

Author: byroot

activerecord/lib/arel/tree_manager.rb

@@ -53,7 +53,7 @@ def to_dot
     def to_sql(engine = Table.engine)
       collector = Arel::Collectors::SQLString.new
       engine.with_connection do |connection|
-        engine.lease_connection.visitor.accept(@ast, collector).value
+        connection.visitor.accept(@ast, collector).value
       end
     end