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

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I623c55df7f8d4f15c3226072449ca4d09a36d67c