Pin timm version in package requirements

[mberr]

For me, fixing the timm version seems to suffice to fix #242 locally.

Other than that I kept the packages that are installed by pip install; for the package versions mentioned in https://github.com/clovaai/donut/#software-installation this means

torch                     2.0.1
torchvision               0.15.2
pytorch-lightning         2.0.9
transformers              4.33.2

Notice that I only tested the cpu version and the demo in app.py, but did not attempt any training.