chore: fix new client command (#11520)

The command is `add-new-library`, not `add-new-client`.

Author: meltsufin

.github/workflows/generate_new_client_hermetic_build.yaml

@@ -105,7 +105,7 @@ jobs:
           Command used:
 
           \`\`\`
-          python generation/new_client_hermetic_build/add-new-client-config.py add-new-client ${GENERATION_ARGUMENTS}
+          python generation/new_client_hermetic_build/add-new-client-config.py add-new-library ${GENERATION_ARGUMENTS}
           
           \`\`\`"
           gh pr create --title "${commit_message}" --label "owlbot:run" --head "${branch_name}" --body "${pr_body}"