Revert "BinaryTransparencyService: Add APEX update observer"

This reverts commit 00001111.

Reason for revert: DroidMonitor: Potential culprit for b/265401181 - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted
Bug: 265401181

Change-Id: I9451eff18a0572677a9478a4d68b8e2cbe36b24d