Update SubscriptionManager API by replacing 'id' & 'idx' with 'index'.

Bug: 35767068
Test: No build failure on update.
Change-Id: I5345fd45f3f5af356f8f033a49c4e512bfc81d66
Merged-in: I5345fd45f3f5af356f8f033a49c4e512bfc81d66
1 file changed