Revert "Revert "Bump cirros version to 0.6.1""

This reverts commit 37d11d00e56ec6ff402a13a28ec308c13291a937.

Reason for revert: reverting this revert as the issue caused by the original patch (before the first revert) is fixed by:
https://review.opendev.org/c/openstack/devstack/+/881504

Therefore we can proceed with the cirros version bump.

Change-Id: I43e2b04a0142c19fb1a79da5a33cc444149e18f1
diff --git a/doc/source/guides/nova.rst b/doc/source/guides/nova.rst
index 5b42797..d0fb274 100644
--- a/doc/source/guides/nova.rst
+++ b/doc/source/guides/nova.rst
@@ -122,7 +122,7 @@
 .. code-block:: shell
 
   $ openstack --os-compute-api-version 2.37 server create --flavor cirros256 \
-      --image cirros-0.3.5-x86_64-disk --nic none --wait test-server
+      --image cirros-0.6.1-x86_64-disk --nic none --wait test-server
 
 .. note:: ``--os-compute-api-version`` greater than or equal to 2.37 is
           required to use ``--nic=none``.