Set py 3.8 as required version

Author: Tatjana Damnjanović

setup.py

@@ -58,6 +58,7 @@
     description='The SolveBio Python client',
     long_description=long_description,
     long_description_content_type='text/markdown',
+    python_requires='>=3.8',
     author='Solve, Inc.',
     author_email='contact@solvebio.com',
     url='https://github.com/solvebio/solvebio-python',