Remove unused module imports from TAP tests

The Config and Cwd modules were no longer used, but remained imported,
in a number of tests.  Remove to keep the imports to the actually used
modules.

Reviewed-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/A5A074CD-3198-492B-BE5E-7961EFC3733F@yesql.se

src/bin/pg_test_fsync/t/001_basic.pl

@@ -4,7 +4,6 @@
 use strict;
 use warnings;
 
-use Config;
 use PostgreSQL::Test::Utils;
 use Test::More;