unpin protobuf after TF is upgraded to 2.21

[github-actions]

See: tensorflow/tensorflow#103382

Line: 165

deepmd-kit/pyproject.toml

Lines 162 to 172 in 4e64f8b

	]
	pin_tensorflow_gpu = [
	"tensorflow==2.18.0",
	# TODO: unpin protobuf after TF is upgraded to 2.21
	# See: https://github.com/tensorflow/tensorflow/pull/103382
	"protobuf<7.34.0",
	]
	pin_pytorch_cpu = [
	# https://github.com/pytorch/pytorch/issues/114602
	# macos x86 has been deprecated
	"torch==2.11.0; platform_machine!='x86_64' or platform_system != 'Darwin'",