Remove unnecessary HashMap instantiation

Was investigating something else, but noticed something that could be a tiny bit better; return an empty map from `Collections.emptyMap` instead of using a real `HashMap` to send an empty one.

Test: Builds successfully

Change-Id: Id11d39d3ea90e15bd4cb90031d6242d8e1f98819
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>

Author: Josep del Rio

telephony/java/android/telephony/TelephonyManager.java

@@ -13971,7 +13971,6 @@ public boolean isEmergencyAssistanceEnabled() {
     @NonNull
     @RequiresFeature(PackageManager.FEATURE_TELEPHONY_CALLING)
     public Map<Integer, List<EmergencyNumber>> getEmergencyNumberList() {
-        Map<Integer, List<EmergencyNumber>> emergencyNumberList = new HashMap<>();
         try {
             ITelephony telephony = getITelephony();
             if (telephony != null) {
@@ -13984,7 +13983,7 @@ public Map<Integer, List<EmergencyNumber>> getEmergencyNumberList() {
             Log.e(TAG, "getEmergencyNumberList RemoteException", ex);
             ex.rethrowAsRuntimeException();
         }
-        return emergencyNumberList;
+        return Collections.emptyMap();
     }
 
     /**