Revert "Add soong config variables for selinux_policy_system in ..."

Revert submission 3172679-selinux_policy_system

Reason for revert: Likely culprit for b/371922616  - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.

Reverted changes: /q/submissionid:3172679-selinux_policy_system

Change-Id: Ia90bc5fef3f3ba71b1637a7906fd3d4d1d0ff6e3