Cleanup usages of MANAGE_ACTIVITY_STACKS permission

1. remove privileged from protectionLevel.
2. remove usages of MANAGE_ACTIVITY_STACKS in gms.

Bug: 63118109
Test: manual
Change-Id: I98f55b2b19f5b19f62926e843ebcef991f8360db
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index cc8927f..fc95ceb 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -2244,7 +2244,7 @@
 
     <!-- @SystemApi @TestApi @hide Allows an application to create/manage/remove stacks -->
     <permission android:name="android.permission.MANAGE_ACTIVITY_STACKS"
-        android:protectionLevel="signature|privileged" />
+        android:protectionLevel="signature" />
 
     <!-- @SystemApi @TestApi @hide Allows an application to embed other activities -->
     <permission android:name="android.permission.ACTIVITY_EMBEDDING"