DO NOT MERGE: Fix ActivityManager#killBackgroundProcesses permissions

In the pevious CL, we incorrectly added the permission check in the
killBackgroundProcessesExcept. Now fix this issue.

Bug: 239423414
Bug: 223376078
Test: atest CtsAppTestCases:ActivityManagerTest
Merged-In: I35d20539ffac055a6d61260445620f45584bd9c5
Merged-In: Ieed6af77da1bc31cfecc5272b9f97971db7ae7b2
Merged-In: I8b8a427ee87339cc038e53adc0912283b05d2cfc
Change-Id: I9471a77188ee63ec32cd0c81569193e4ccad885b