Add nvidia runtimeClass to device plugin DaemonSet

The device plugin needs access to NVIDIA libraries (NVML) to discover
GPUs. Running with the nvidia runtime makes device files visible.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

argocd/manifests/nvidia-device-plugin/daemonset.yaml

@@ -19,6 +19,7 @@ spec:
         - key: nvidia.com/gpu
           operator: Exists
           effect: NoSchedule
+      runtimeClassName: nvidia
       priorityClassName: system-node-critical
       containers:
         - name: nvidia-device-plugin