Remove the restart handlers for lms cms and lms-preview.

These handlers aren't being used by anyone and have been superceded by
the handler that starts and stops all edxapp components.

playbooks/roles/gunicorn/handlers/main.yml

----
-- name: restart lms
-  service: name=lms state=restarted
-  sudo: True
-
-- name: restart cms
-  service: name=cms state=restarted
-  sudo: True
-
-- name: restart lms-preview
-  service: name=lms-preview state=restarted
-  sudo: True