Update the README description

Carrier_list.pb move to latest_carrierid/ folder, so update the
description.

Bug: 155254987
Test: Build pass
Change-Id: I389838a3e6413079301e852880e075dbcf4ee533
diff --git a/etc/README b/etc/README
index 08233dc..9fcab8d 100644
--- a/etc/README
+++ b/etc/README
@@ -16,4 +16,4 @@
 
 For APNs with a matching carrier ID please assign a carrier ID
 AOSP carrier ID assignments can be found at
-https://android.googlesource.com/platform/packages/providers/TelephonyProvider/+/master/assets/carrier_list.textpb
\ No newline at end of file
+https://android.googlesource.com/platform/packages/providers/TelephonyProvider/+/master/assets/latest_carrier_id/carrier_list.textpb