Remove legacy fontations png code

Client CL:
 - https://crrev.com/c/6607867

Change-Id: I100f2ac4f946ecb5b481496b664568dad6695278
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1001897
Reviewed-by: Daniel Dilan <danieldilan@google.com>
Auto-Submit: Kaylee Lubick <kjlubick@google.com>
Commit-Queue: Kaylee Lubick <kjlubick@google.com>
1 file changed