CI: Fix TestFunctions

- Use 'use parent' instead of '@ISA'
- Add Perl::Critic leniency

t/TestFunctions.pm

@@ -14,7 +14,9 @@ use File::Basename qw/
 require File::Temp;
 
 use Exporter;
-our @ISA = qw/ Exporter /;
+use parent 'Exporter';
+## no critic ( Modules::ProhibitAutomaticExportation )
+# This is a test function library, it's not production code...
 our @EXPORT = qw/
     are_hardlinked
     file_exists