pgsql: Reduce warnings with -Wshadow=compatible-local builds

Reduce warnings with -Wshadow=compatible-local builds

In a similar effort to f01592f91, here we further reduce the warnings we
get about local variables being shadowed when building with
-Wshadow=compatible-local.  This small change reduces the overall number
of warnings by 36.

Discussion: https://postgr.es/m/CAApHDvqBBqF=wmV5azrO7h3VwpwQo+JFBQ+g=E6wVUhKcqR8gA@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/92fce4e1eda9b24d73f583fbe9b58f4e03f097a4

Modified Files
--------------
src/test/regress/regress.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)