Cleaned up the deprecated APIs

Bug: 270094276
Test: Basic phone funcationality tests
Change-Id: Iffae0504a47718525152bc28f3cad2657b542362
diff --git a/src/com/android/phone/ImsProvisioningController.java b/src/com/android/phone/ImsProvisioningController.java
index 6a6b155..a62980e 100644
--- a/src/com/android/phone/ImsProvisioningController.java
+++ b/src/com/android/phone/ImsProvisioningController.java
@@ -1564,13 +1564,7 @@
     }
 
     protected int getSubId(int slotId) {
-        final int[] subIds = mSubscriptionManager.getSubscriptionIds(slotId);
-        int subId = SubscriptionManager.INVALID_SUBSCRIPTION_ID;
-        if (subIds != null && subIds.length >= 1) {
-            subId = subIds[0];
-        }
-
-        return subId;
+        return SubscriptionManager.getSubscriptionId(slotId);
     }
 
     protected int getSlotId(int subId) {