May need to remove pillow<7 from requirements.txt

[wangkuiyi]

Following steps listed in https://github.com/iree-org/iree-torch#running-end-to-end-correctness-tests, I ran

python -m pip install -r requirements.txt

It gave me the following errors.

  note: This error originates from a subprocess, and is likely not a problem with pip.
  Rolling back uninstall of Pillow
  Moving to /Users/y/miniforge3/envs/torch-mlir/lib/python3.10/site-packages/PIL/
   from /Users/y/miniforge3/envs/torch-mlir/lib/python3.10/site-packages/~IL
  Moving to /Users/y/miniforge3/envs/torch-mlir/lib/python3.10/site-packages/Pillow-9.4.0.dist-info/
   from /Users/y/miniforge3/envs/torch-mlir/lib/python3.10/site-packages/~illow-9.4.0.dist-info
error: legacy-install-failure

It turns out that a contemporary version of pillow is 9.4.0. However, requirements.txt wants version <7.

iree-torch/requirements.txt

Line 23 in 5fbaf50

pillow<7