Add pyinotify to development requirements for docker devstack perf

Django can use pyinotify for watching files in runserver which should
save a lot of CPU work in docker.

requirements/edx/development.txt

@@ -10,6 +10,7 @@
 
 click==3.3
 isort==4.2.5
+pyinotify==0.9.6
 
 # Third-party:
 -e git+https://github.com/doctoryes/code_block_timer.git@f3d0629f086bcc649c3c77f4bc5b9c2c8172c3bf#egg=code_block_timer