photonlibpy: License under MIT (#1700)

Everything under the `photon-lib` directory is intended to all be
licensed under MIT:


e40c8fbca0/photon-lib/.styleguide-license (L2)

Presumably we don't want to force teams to release their robot code
under GPL.

photon-lib/py/setup.py

@@ -71,4 +71,7 @@ setup(
     author="Photonvision Development Team",
     long_description="A Pure-python implementation of PhotonLib",
     long_description_content_type="text/markdown",
+    classifiers=[
+        "License :: OSI Approved :: MIT License",
+    ],
 )