Fix NPE due to SparseArray.remove() without gc().

This is a follow-up to ag/23216745 where we missed one method that is
removing elements from SparseArray. It is calling remove() instead of
removeReturnOld() because we don't need the old value and may get
slightly better performance.

Fixes: 295856715
Bug: 263504888
Test: presubmit
Change-Id: I9ce0a9cc4571b343debfc4f0cfce3ea351f2f1a7