cmd/k8s-operator: use our own container image instead of busybox

We already have sysctl in the `tailscale/tailscale` image, just use that.

Updates #cleanup

Signed-off-by: Maisem Ali <maisem@tailscale.com>

docs/k8s/proxy.yaml

@@ -11,7 +11,7 @@ spec:
     # the container. The `net.ipv4.ip_forward` sysctl is not allowlisted
     # in Kubelet by default.
   - name: sysctler
-    image: busybox
+    image: "ghcr.io/tailscale/tailscale:latest"
     securityContext:
       privileged: true
     command: ["/bin/sh"]