Revert "Use Apex sepolicy if it's available"

Revert "Build precompiled_sepolicy.apex_sepolicy.sha256"

Revert submission 1965099-precompiled-apex-sepolicy

Reason for revert: Boot regression b/217252559
Reverted Changes:
I2dbe43e32:Use Apex sepolicy if it's available
Bug: 217252559

Change-Id: I1cca3a1ae833c21619de26b2610736170ec5463c