Revert "SystemUI: Add data type and signal icons"

* These aren't used anywhere and are still Holo

This reverts commit 4e5e6d4cd8e56755d3e4cdaf08ede0e7ee3c82dc.

Change-Id: I39c6060766b2f75dd1362d945be31f6f9d20f59d
(cherry picked from commit e3a5a496e1bbe3a8e9b3e82b61b465e828c09b5b)