Update Spack reference format in workflow

Author: rem1776

.github/workflows/github_cmake_nvhpc.yml

@@ -25,7 +25,7 @@ jobs:
       uses: spack/setup-spack@v3.0.0
       with:
         buildcache: true
-        spack_ref: releases/v1.1.1
+        spack_ref: v1.1.1
         packages_ref: v2026.03.0
     - name: Set up custom build cache and build compiler
       run: |