Remove email field from CS client user object

This requires cs_comments_service commit 1d50176.

lms/lib/comment_client/user.py

@@ -6,14 +6,14 @@ import settings
 
 class User(models.Model):
 
-    accessible_fields = ['username', 'email', 'follower_ids', 'upvoted_ids', 'downvoted_ids',
+    accessible_fields = ['username', 'follower_ids', 'upvoted_ids', 'downvoted_ids',
                          'id', 'external_id', 'subscribed_user_ids', 'children', 'course_id',
                          'subscribed_thread_ids', 'subscribed_commentable_ids',
                          'subscribed_course_ids', 'threads_count', 'comments_count',
                          'default_sort_key'
                         ]
 
-    updatable_fields = ['username', 'external_id', 'email', 'default_sort_key']
+    updatable_fields = ['username', 'external_id', 'default_sort_key']
     initializable_fields = updatable_fields
 
     metric_tag_fields = ['course_id']
@@ -26,8 +26,7 @@ class User(models.Model):
     def from_django_user(cls, user):
         return cls(id=str(user.id),
                    external_id=str(user.id),
-                   username=user.username,
-                   email=user.email)
+                   username=user.username)
 
     def follow(self, source):
         params = {'source_type': source.type, 'source_id': source.id}