Bug 24693: Move GD from recommends to requires in cpanfile

Bug 24693: Move GD from recommends to requires in cpanfile

Without it, catalogue/detail.pl dies (and probably other scripts too)

Test plan:
1. Uninstall GD, reload starman
2. Go to catalogue/detail.pl. Confirm that it dies
3. Reinstall GD, reload starman
4. Go to catalogue/detail.pl. Confirm that it work normally

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>