Do not chmod ANRs

The code was only meant for native tombstones. It might be a good idea
to make ANRs also readable by shell / adb, but in that case we have to
do more changes to make sure all files in /data/anr are. We can revert
if we implement that

Test: m
Bug: 329827513
Change-Id: Ic98c452ca500fe766a70173bef4ac1ea57438989