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/test/perl/PostgreSQL/Test/Cluster.pm

@@ -93,7 +93,6 @@ use warnings;
 
 use Carp;
 use Config;
-use Cwd;
 use Fcntl qw(:mode);
 use File::Basename;
 use File::Path qw(rmtree);