Remove exported2_system_prop

It's not used anymore.

Bug: 161659925
Test: boot
Change-Id: I5b08bdace28a509d464759a66025c951178225c6
Merged-In: I5b08bdace28a509d464759a66025c951178225c6
(cherry picked from commit 7d96ddbfb0b2e34c79b921538bebcaaf35c988ff)
8 files changed