Revert "Adds install source checks for accessibility service"

This reverts commit f1f2c847560e7ebb741909bd398c7d220d5078dc.
The stragery is chaged, we don't need to check the installer
nor if it is sytem app. We also delete the tests that are
obsolete.

Bug: 221318082
Test: AccessibilitySecurityPolicyTest, PolicyWarningUIControllerTest
Change-Id: Ide89213dbf90cdb57001e5b05a2eeefc35f6adee
5 files changed