FreeSolv database is wrong

[GregorySchwing]

🐛 Bug

The dataset used to load the FreeSolv database is not correct.

To Reproduce

Steps to reproduce the behavior:

1. Download csv of deepchem's FreeSolv
   https://deepchemdata.s3.us-west-1.amazonaws.com/datasets/freesolv.csv.gz
2. Download csv of Mobley's FreeSolv csv
   https://github.com/MobleyLab/FreeSolv/blob/master/database.txt
3. Cross reference the first molecule in deepchem by smile string

Deepchem
smiles                     y 
CN(C)C(=O)c1ccc(cc1)OC    -1.8744673709079

Mobley
smiles                     experimental value (kcal/mol) 
CN(C)C(=O)c1ccc(cc1)OC    -11.01

Expected behavior

Match reference.

[rbharath]

It's possible the deepchem version may be pre-normalized. We should check by plotting the distributions.

CC @ARY2260