gplugin/gplugin

Fix some perl5 loader names that were missed in the perl->perl5 rename

Testing Done:
Ran the unit tests and veried the info was correct with `gplugin-query`.

Reviewed at https://reviews.imfreedom.org/r/934/
[wrap-git]
directory=gi-docgen
url=https://gitlab.gnome.org/GNOME/gi-docgen.git
push-url=ssh://git@gitlab.gnome.org:GNOME/gi-docgen.git
revision=main
depth=1