docs: api_extension: Remove links to the stale example patches
docs: api_extension: Remove links to the stale example patches

The patches used as an example for the api_extension manual don't hold
up to the current standards any more. Carefully remove links and
mentions of the patches from the docs.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

olafhering/libvirt,libvirt/libvirt,andreabolognani/libvirt,eskultety/libvirt,olafhering/libvirt,jardasgit/libvirt,olafhering/libvirt,jfehlig/libvirt,jfehlig/libvirt,nertpinx/libvirt,zippy2/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,zippy2/libvirt,nertpinx/libvirt,nertpinx/libvirt,andreabolognani/libvirt,crobinso/libvirt,jardasgit/libvirt,crobinso/libvirt,jardasgit/libvirt,olafhering/libvirt,fabianfreyer/libvirt,zippy2/libvirt,jardasgit/libvirt,eskultety/libvirt,crobinso/libvirt,libvirt/libvirt,eskultety/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,libvirt/libvirt,fabianfreyer/libvirt,crobinso/libvirt,andreabolognani/libvirt,nertpinx/libvirt,eskultety/libvirt,libvirt/libvirt,andreabolognani/libvirt,jfehlig/libvirt,zippy2/libvirt,eskultety/libvirt