Modified Variable name to be consistent across all blueprint

Author: LAVEEN

examples/machine-learning/a4x-highgpu-4g/a4xhigh-slurm-blueprint.yaml

@@ -143,7 +143,7 @@ deployment_groups:
           #!/bin/bash
           set -e -o pipefail
           ansible-pull \
-              -U https://github.com/GoogleCloudPlatform/slurm-gcp -C $(vars.build_from_git_ref) \
+              -U https://github.com/GoogleCloudPlatform/slurm-gcp -C $(vars.build_slurm_from_git_ref) \
               -i localhost, --limit localhost --connection=local \
               -e @/var/tmp/slurm_vars.json \
               ansible/playbook.yml