[automerger skipped] Remove unused methods File{Input,Output}Stream.open(). am: 5d9a26d38c am: 48e47b16c6 am: 092e1fb6fc -s ours

am skip reason: Change-Id I0e4ec21a0686eb151d2da2eb0c11def70921b3e9 with SHA-1 5d9a26d38c is in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/libcore/+/10843578

Change-Id: I45c6c298a84e6c3c24bbcc425f323b297696552f