Post cancelAsUser to mHandler.

This is to fix a java.lang.SecurityException: Caller android:1010157 cannot post for pkg android in user 10
that was coming from this line.

Bug: 153016511
Test: Manual - did make, flash, ran a test app to repro the SecurityException to verify it does not.
Change-Id: Icb1bb9982a7fb4b377b0b6773c19a146c5ea8f63

services/core/java/com/android/server/biometrics/face/FaceService.java

@@ -379,8 +379,10 @@ public class FaceService extends BiometricServiceBase {
             checkPermission(MANAGE_BIOMETRIC);
             updateActiveGroup(userId, opPackageName);
 
-            mNotificationManager.cancelAsUser(NOTIFICATION_TAG, NOTIFICATION_ID,
-                    UserHandle.CURRENT);
+            mHandler.post(() -> {
+                mNotificationManager.cancelAsUser(NOTIFICATION_TAG, NOTIFICATION_ID,
+                        UserHandle.CURRENT);
+            });
 
             final boolean restricted = isRestricted();
             final EnrollClientImpl client = new EnrollClientImpl(getContext(), mDaemonWrapper,