temp/gnome-software: break cyclic dependency with own plugin

Depencency chain:

gnome-software -> gnome-softare-plugin-apk -> gnome-software-lib -> gnome-software

is broken.

Application should not depend on its own plugin, instead plugin should probably be installed using install_if="gnome-software apk-tools".

This is needed to unblock BPO:

master/x86_64/gnome-software-9999_git20211203-r0.apk (missing depends: gnome-software)
master/aarch64/gnome-software-9999_git20211203-r0.apk (missing depends: gnome-software)
master/armv7/gnome-software-9999_git20211203-r0.apk (missing depends: gnome-software)
master/armhf/gnome-software-9999_git20211203-r0.apk (missing depends: gnome-software)
master/x86/gnome-software-9999_git20211203-r0.apk (missing depends: gnome-software) 

See also:

• https://gitlab.alpinelinux.org/alpine/aports/-/blob/master/community/discover/APKBUILD#L91
• https://gitlab.alpinelinux.org/alpine/aports/-/blob/master/community/discover/APKBUILD#L104

which works perfectly fine.

pmbootstrap can't build g-s because to build g-s it should first build g-s-plugin-apk, which depends on g-s-lib (see p.a.o expand "Depends" column on the right), which is.. part of g-s, 💣️ 💥 so pmb needs to build g-s first, which it can't do, because... you see, to understand a recursion, you first need to understand a recursion