Remove the platform VPN use case from the FGS type "systemExemption"

VPN apps using the platform-based VPN APIs don't need to run a FGS
to keep the VPN active.

Bug: 267820824
Test: atest CtsAppFgsTestCases
Change-Id: I35eed3c55253c2d8b100a2b2c7c2c3445708073f

core/java/android/app/ForegroundServiceTypePolicy.java

@@ -388,7 +388,6 @@ public abstract class ForegroundServiceTypePolicy {
                 new RegularPermission(Manifest.permission.SCHEDULE_EXACT_ALARM),
                 new RegularPermission(Manifest.permission.USE_EXACT_ALARM),
                 new AppOpPermission(AppOpsManager.OP_ACTIVATE_VPN),
-                new AppOpPermission(AppOpsManager.OP_ACTIVATE_PLATFORM_VPN),
             }, false)
     );