news: Document apparmor improvements in v6.7.0
news: Document apparmor improvements in v6.7.0

Add news about apparmor improvements.

Signed-off-by: Jianan Gao <d3f377dd55bf6fdae8b936ff4bda5bc66bfe5c38@redhat.com>
Reviewed-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>

crobinso/libvirt,libvirt/libvirt,libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt,zippy2/libvirt,zippy2/libvirt,jfehlig/libvirt,olafhering/libvirt,olafhering/libvirt,libvirt/libvirt,zippy2/libvirt,nertpinx/libvirt,jfehlig/libvirt,olafhering/libvirt,jfehlig/libvirt,libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt,crobinso/libvirt,crobinso/libvirt,crobinso/libvirt,jfehlig/libvirt,olafhering/libvirt,zippy2/libvirt