update selfhost runner logic

Author: sandeepgupta12

.github/workflows/ppc64le.yml

@@ -39,6 +39,6 @@ jobs:
     with:
       build-environment: linux-ppc64le-binary-manywheel
       docker-image-name: pytorch-ppc64le:ubi9.3
-      runner_prefix: 'self-hosted,'  # Example prefix
+      runner_prefix: '[self-hosted,'  # Example prefix
       runner: 'linux,'               # Example runner
-      runner-ppc64le: 'ppc64le'      # Specific architecture
+      runner-ppc64le: 'ppc64le]'      # Specific architecture