Change trace tag for AppOpsCheckingServiceTracingDecorator

"Trace.TRACE_TAG_SYSTEM_SERVER" is used here as a trace category. This is probably fine, but, CrystalBall itself isn't currently configured to log this category.

As a workaround, use the trace tag "Trace.TRACE_TAG_ACTIVITY_MANAGER" instead.

Later, we might want to change this back to "Trace.TRACE_TAG_SYSTEM_SERVER" (or even create a new tag for permissions), and configure CrystalBall to support this category.

Bug: 252887420
Change-Id: Ia9ade03369de94ece045ec1433c9797e8eb8ce1e
Test: CrystalBall CUJ: android.platform.test.scenario.permissions.PermissionsTest