purge: fix symlink to purge-container-cluster

ceph/ceph-ansible#4805 introduced a symlink to
purge-container-cluster.yml playbook which is broken.

This commit fixes it.

Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>

diff --git a/infrastructure-playbooks/purge-docker-cluster.yml b/infrastructure-playbooks/purge-docker-cluster.yml
index 13c6fb0853b9246f5fb0bce4e38fcb1ef5aee3c4..0d30f194d3efcc2a55b293103c7068721b5169be 120000 (symlink)
--- a/infrastructure-playbooks/purge-docker-cluster.yml
+++ b/infrastructure-playbooks/purge-docker-cluster.yml
@@ -1 +1 @@
-infrastructure-playbooks/purge-container-cluster.yml
\ No newline at end of file
+purge-container-cluster.yml
\ No newline at end of file