Upgrade fonttools to 4.15.0 am: c9804561ed am: 6baeafbb6d am: 4f502262a1 am: 2d54a34c1c

Original change: https://android-review.googlesource.com/c/platform/external/fonttools/+/1433028

Change-Id: Ia36ca2d20fbfa25340019540a86c1e46b49b98f8