Update edx-drf-extensions to 2.0.0.

Note: this version update is backward incompatible.

ARCH-255

cms/djangoapps/api/v1/views/course_runs.py

@@ -1,6 +1,6 @@
 from django.conf import settings
 from django.http import Http404
-from edx_rest_framework_extensions.authentication import JwtAuthentication
+from edx_rest_framework_extensions.auth.jwt.authentication import JwtAuthentication
 from opaque_keys.edx.keys import CourseKey
 from rest_framework import parsers, permissions, status, viewsets
 from rest_framework.authentication import SessionAuthentication