docs: Fix clustermesh secrets namespace
docs: Fix clustermesh secrets namespace

The other commands in this doc specify the namespace, but the creation
of the clustermesh configuration doesn't. I found that without
specifying this, the configuration was not properly mounted into the
cilium containers.

Signed-off-by: Joe Stringer <16a9a54ddf4259952e3c118c763138e83693d7fd@cilium.io>

cilium/cilium,michi-covalent/cilium,cilium-team/cilium,tklauser/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,tklauser/cilium,tgraf/cilium,michi-covalent/cilium,cilium-team/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,tgraf/cilium,michi-covalent/cilium,cilium/cilium,michi-covalent/cilium