Remove libcore usage of IoUtils.close()

A tidy-up noticed while inspecting IoUtils. IoBridge calls
IoUtils, which calls IoBridge. IoUtils.close() can be
inlined. AFAICT, they weren't always equivalent but they are
now.

Eventually it may be possible to remove IoUtils.close().

Bug: 111055375
Test: build only
Change-Id: I8823c0cb5cef6da009174806e8987842ec289f52