fix: cuda: concretizer: unify: true; single epic

Author: wdconinc

spack-environment/cuda/spack.yaml

@@ -3,8 +3,6 @@ spack:
   - ../concretizer.yaml
   - ../packages.yaml
   - ../view.yaml
-  concretizer:
-    unify: when_possible # multiple epic versions
   specs:
   - acts +cuda cuda_arch=75
   - actsvg