generate.pl: prefer to use VERSION with numeric form

As stated in `perldoc -f use`, using a v-string literal should be
avoided in favor of numeric form for backwards compatibility.

generate.pl

@@ -1,5 +1,5 @@
 #!/usr/bin/env perl
-use v5.14;
+use 5.014;
 use strict;
 use warnings;
 use YAML::XS;