Pin minimum PyTorch version for BLOOM ONNX export
# What does this PR do?

Due to the deprecation of `position_ids` in https://github.com/huggingface/transformers/pull/18342, the BLOOM ONNX export fails unless the `torch` version is >= 1.12

This PR fixes that by pinning the minimum required version in the ONNX configuration (the user gets a warning now).

_The documentation is not available anymore as the PR was closed or merged._