chore: remove Python minor version

Python 3.8 is currently not available on Mac, making the installation
hard for development purpose

Pipfile

@@ -14,4 +14,4 @@ tabulate = "*"
 numpy = ">=1.17.0,<2.0.0"
 
 [requires]
-python_version = "3.8"
+python_version = "3"