Update minimum Python version in python_requires

Author: nateprewitt

setup.py

@@ -16,7 +16,7 @@
     scripts=['bin/jp.py'],
     packages=find_packages(exclude=['tests']),
     license='MIT',
-    python_requires='>=3.7',
+    python_requires='>=3.9',
     classifiers=[
         'Development Status :: 5 - Production/Stable',
         'Intended Audience :: Developers',