Fix typo in libartbase mem_map.h am: 999465fda7 am: 92cdc984d0 am: 88c2304ce0

Original change: https://android-review.googlesource.com/c/platform/art/+/2460088

Change-Id: Ia5971493acd86af47772b31068502691fcc08711
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>