docs: fix typo cillium -> cilium in encryption-ztunnel.rst

The example kubectl command in the mTLS/ztunnel encryption validation section referenced `<cillium-pod-hosting-mtls-pod>` with a doubled l. Correct it to `<cilium-pod-hosting-mtls-pod>` so the placeholder matches the project name and is clearer to readers following the validation steps.

Signed-off-by: Chikkala Kiran babu <chikkalakiranbabu1@gmail.com>

Author: kiranbabu23

Documentation/security/network/encryption-ztunnel.rst

@@ -144,7 +144,7 @@ Validate the Setup
    processed by the enrollment reconciler.
 
 #. Run a ``bash`` shell in one of the Cilium pods hosting a mtls-enrolled pod with
-   ``kubectl -n kube-system exec -ti pod/<cillium-pod-hosting-mtls-pod> -- bash`` 
+   ``kubectl -n kube-system exec -ti pod/<cilium-pod-hosting-mtls-pod> -- bash``
    and execute the following commands:
 
    Install tcpdump