Upgrade fonttools to 4.20.0 am: 20c690aa8c am: 6e1560f5dc am: d47a0690f7 am: 013c93c250

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I97109c59995c62461fe649abbc5d12af9fa6ab34