fix(course): return avatar url without absolute uri

Use avatar.url directly to avoid duplicating the host when the
storage returns an absolute URL. Prevents malformed avatar links
in live session token responses.

apps/course/views/live_session.py

@@ -272,5 +272,5 @@ class CourseLiveSessionTokenAPIView(GenericAPIView):
     def _build_profile_url(request, user):
         avatar = getattr(user, 'avatar', None)
         if avatar and getattr(avatar, 'url', None):
-            return request.build_absolute_uri(avatar.url)
+            return avatar.url
         return None