Fix py-torch build

PyTorch 1.9.1 (fixed in versions >= 1.10.0) depends on an older onnx
version that utilizes a deprecated function from Google's protobuf
library that was removed in version 3.18.0 (see
https://github.com/protocolbuffers/protobuf/pull/8794/).

Workaround by specifying an explicit version range for this
dependency.

spack.yaml

@@ -32,5 +32,5 @@ spack:
     # demo for codejam12
     - funniest1022 %gcc@10.3.0
     # NRP
-    #- py-torch~mkldnn~cuda~cudnn~onnx_ml %gcc@10.3.0
+    - py-torch~mkldnn~cuda~cudnn~onnx_ml ^protobuf@:3.17.999 %gcc@10.3.0
   concretization: together