package/perl-gd: drop gdlib-config

Drop gdlib-config as it won't be available after the bump to version
2.3.0. If gdlib-config is not available, perl-gd fallbacks on glibc.pc
since version 2.57:
https://github.com/lstein/Perl-GD/commit/069e6cfff61e10c71474d75ed20d2ca11abc8f0e



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>