[framework] Remove boot complete marker

ART doesn't load the boot image from /data anymore and the marker is
useless.

Test: device boots
Bug: 143899228

(cherry picked from commit 46a81bda)

Merged-In: I7104b961d2fc2de53ffea4c14cce6b785ff534dd
Change-Id: I7104b961d2fc2de53ffea4c14cce6b785ff534dd