Update FontTools to 4.31.2 to gain access to iterSubTables. am: 0b59a54a78 am: 3e24ea754b am: 3886b0a80e

Original change: https://android-review.googlesource.com/c/platform/external/fonttools/+/2043270

Change-Id: Ie02c14d6e2550eb53669c28030dcf2c938419d6e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>