Update requirements.txt to include only the main packages

[naga-karthik]

Reinstalling the existing requirements.txt in a separate virtual environment resulted in dependency errors and some packages not being installed. This is mainly due to pip freeze dumping all the packages in the virtual env leading to dependency clashes.

The updated requirements.txt is as follows:

torch==1.8.1+cu111
torchvision==0.9.1+cu111
monai==0.9.0
nibabel==3.2.2
num2words==0.5.11
numpy==1.22.4
ivadomed==2.9.6
wandb==0.12.18
scikit-image==0.19.3
scikit-learn==1.1.2
scipy==1.8.1
seaborn==0.12.0
pytorch-lightning==1.6.4

Check out the pipreqs package as suggested here to avoid dumping all the packages in requirements.txt