Add PrintSpooler to system app whitelist

This app builds directly against the platform. Add it to the whitelist.

Bug: 64382372
Test: make
Test: device boots
Change-Id: Ia77df2db78adf62a525f08549d71360924f1a3f6
Merged-In: I4c308d93d66391da2d3691eb45e5d7b1c1fdd582
(cherry picked from commit f7e625c1)