chore: spack: avoid need for protobuf +cpp

This cherry-picks the upstream work on making protobuf +cpp unnecessary, enabling us to upgrade some python components.

spack.sh

@@ -30,6 +30,7 @@ a66586d749197841bd74e289802126f2359287a8
 7503a417731910d918a7863d1862f62c9b76429d
 f8f01c336c882f29ac364995423b9f69ac365462
 6051d56014730528da8dfa69934d93f9b7941a70
+096ab11961995ac8d69f7b177cbcadf618d3068e
 6c4abef75cb2b98c337f8a3179797e29dfdc9ca3
 ---
 ## Optional hash table with comma-separated file list
@@ -60,4 +61,5 @@ read -r -d '' SPACK_CHERRYPICKS_FILES <<- \
 ## 7503a417731910d918a7863d1862f62c9b76429d: cuda: add v12.4.1
 ## f8f01c336c882f29ac364995423b9f69ac365462: clang: support cxx20_flag and cxx23_flag
 ## 6051d56014730528da8dfa69934d93f9b7941a70: fastjet: avoid plugins=all,cxx combinations
+## 096ab11961995ac8d69f7b177cbcadf618d3068e: py-onnx: link to external protobuf
 ## 6c4abef75cb2b98c337f8a3179797e29dfdc9ca3: py-protobuf: drop +cpp, always require protobuf