remove keras

from requirements and environment

environment.yml

 name: dfpl_env
 channels:
   - conda-forge
-  - bioconda
 dependencies:
   - python=3.8.2
   - pip=20.1.1
@@ -11,7 +10,6 @@ dependencies:
   - tensorflow >=2.7,<2.8
   - scikit-learn=0.23.1
   - pandas=1.0.5
-  - keras=2.4.3
   - rdkit=2020.03.4
   - matplotlib=3.2.2
   - pytest=5.4.3

requirements.txt

 jsonpickle==1.4.1
 pandas==1.0.5
 rdkit-pypi==2020.9.5.2 
-keras==2.4.3
 tensorflow==2.2.0
 scikit-learn==0.23.1
 matplotlib==3.2.2