GH actions spack.yaml bug fix.

Author: nkoukpaizan

.github/workflows/spack_cpu_build.yaml

@@ -137,7 +137,7 @@ jobs:
                 padded_length: False
             mirrors:
               local-buildcache: oci://${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
-            spack: https://binaries.spack.io/develop
+              spack: https://binaries.spack.io/develop
             packages:
               all:
                 require: "%gcc"