Drop libapparmor dependency from build docs

As of opencontainers/runc@db093f6 runc no longer depends on libapparmor
thus libapparmor-dev no longer needs to be installed to build it or
anythind that depends on it (like containerd or cri-containerd). Adjust
the documentation accordingly.

containerd/containerd#2238 did the same for containerd.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

contrib/ansible/tasks/bootstrap_ubuntu.yaml

@@ -8,7 +8,6 @@
       - tar
       - apt-transport-https
       - btrfs-tools
-      - libapparmor1
       - libseccomp2
       - socat
       - util-linux