Bump pytorch version to 1.12

[gsakkis]

Bump pytorch to 1.12 to support torchdata introduced in #173:

• torchdata is available for torch 1.11 or later. This was not caught by the CI when testing against torch 1.10 because torchdata was installed after torch and triggered a reinstallation to the latest version (1.12).
• the ShardingFilter of torchdata doesn't seem to work at version 0.3 (required for torch 1.11); all data are processed by all workers. In torchdata 0.4 / torch 1.12 sharding works correctly.

Also torch 1.12 has better support than 1.11 for sparse CSR tensors. The pytorch_data_api_tiledb_sparse.ipynb example notebook fails at the last cell on torch 1.11 if TensorKind.SPARSE_CSR (default for 2D sparse arrays) is passed in ArrayParams.