Bump minimum protobuf version to 31.0-rc1

See jvolkman/rules_pycross#209

The old protobuf version still needs Python 3.8, so attempting to load it fails. I see there is already a PR here (bazel-contrib#3367) but this is a much smaller change for an isolated issue.

Author: Ahajha

MODULE.bazel

@@ -11,7 +11,7 @@ bazel_dep(name = "platforms", version = "0.0.11")
 
 # Those are loaded only when using py_proto_library
 # Use py_proto_library directly from protobuf repository
-bazel_dep(name = "protobuf", version = "29.0-rc2", repo_name = "com_google_protobuf")
+bazel_dep(name = "protobuf", version = "31.0-rc1", repo_name = "com_google_protobuf")
 
 rules_python_config = use_extension("//python/extensions:config.bzl", "config")
 use_repo(