www/py-drf-yasg: Update to 1.16.1

Changelog:

• Fixed compatibility with Django REST framework 3.10.x
• Improved enum type detection for nested "ChoiceFields"

https://github.com/axnsan12/drf-yasg/tree/1.16.1

PR: 240410
Submitted by: Zane C. Bowers-Hadley <vvelox@vvelox.net>