Missing scikit-learn dependency for PD1 benchmark

[Bronzila]

When I try to run the PD1 benchmark cifar100_wideresnet_2048, I get the error that sklearn is required for xgboost. After installing scikit-learn manually, everything works fine. It is simply missing in the dependencies or I messed something up during installation.

Steps to reproduce/How I installed MFPBench:

1. Setup new conda env: conda create --name mfp_test python=3.8
2. Activate environment: conda activate mfp_test
3. Install mf-prior-bench: pip install mf-prior-bench[pd1]

Now when querying the benchmark it returns the error ImportError: sklearn needs to be installed in order to use this module.

After manually installing via pip install scikit-learn everything works fine.

Please let me know if I messed something up when setting up mfpbench :)