Loosen or update protobuf pinned version

**Describe the feature you'd like**
`protobuf` is currently pinned to `"protobuf>=3.9.2,<=3.20.3"` in https://github.com/aws/sagemaker-training-toolkit/blob/859d0198d3979f59fc22a24c0b6cf4860e241045/setup.py#L43C5-L43C31. This prevents installation of other packages that require a higher protobuf version, e.g. http://github.com/onnx/onnx/releases/tag/v1.18.0 which requires `>=4.25.1`.

**How would this feature be used? Please describe.**
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**Describe alternatives you've considered**
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**Additional context**
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Review the protobuf requirement in setup.py at the referenced line and compare it with the compatibility need described for ONNX v1.18.0. Determine an appropriate updated constraint, then verify that the package metadata allows installation alongside packages requiring protobuf >=4.25.1.

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