Upgrade fonttools to 4.20.0 am: 20c690aa8c am: 6e1560f5dc am: d47a0690f7

Original change: https://android-review.googlesource.com/c/platform/external/fonttools/+/1592900

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I652a9d7b79547d55c06727fe308fb54fada2619a