Simplify version check for SKIP clause

Simplify version check for SKIP clause

Checking for the required versions of IO::Pty as well as IPC::Run
can be achieved with a single eval call, and by using the VERSION
function the comparison is guaranteed to follow the same rules as
calling 'use' on the module with a version.

Reported-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/6d880ea2-f8ca-f458-4dcd-a7a3e6d6cd7c@dunslane.net