Fix requirements for python 3.6
pytest==6.2.5
-scikit-learn==1.0
+scikit-learn==1.0 ; python_version >= '3.7'
+scikit-learn==0.24 ; python_version == '3.6'
pandas==1.1.5 ; python_version <= '3.6'
pandas==1.2.2 ; python_version >= '3.7'
