Keep perl style checker happy

It doesn't like code before "use strict;".

(cherry picked from commit ed2c2d063b)

src/backend/catalog/genbki.pl

@@ -14,15 +14,15 @@
 #
 #----------------------------------------------------------------------
 
+use strict;
+use warnings;
+
 use File::Basename;
 use File::Spec;
 BEGIN  { use lib File::Spec->rel2abs(dirname(__FILE__)); }
 
 use Catalog;
 
-use strict;
-use warnings;
-
 my @input_files;
 our @include_path;
 my $output_path = '';