The same condition was repeated twice when comparing the connection used
by existing declared statement with the one coming from a fresh DECLARE
statement.  This had no consequences, but let's keep the code clean.
Oversight in f576de1.

Author: Shenhao Wang
Discussion: https://postgr.es/m/OSBPR01MB42149653BC0AB0A49D23C1B8F2C69@OSBPR01MB4214.jpnprd01.prod.outlook.com
Backpatch-through: 14