pgsql: Doc: Fix incorrect mention to connection_object in CONNECT comma

Doc: Fix incorrect mention to connection_object in CONNECT command of ECPG

This fixes an inconsistency with this parameter name not listed in the
command synopsis, and connection_name is the parameter name more
commonly used in the docs for ECPG commands.

Reported-by: Yusuke Egashita
Discussion: /messages/by-id/156870956796.1259.11456186889345212399@wrigleys.postgresql.org
Backpatch-through: 9.4

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/bec847d9e946ab6e05a2884e524c3cc8c52feebb

Modified Files
--------------
doc/src/sgml/ecpg.sgml | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)