[M144] Remove serialization of drawables from SkCustomTypeface

Original change's description:
> Remove serialization of drawables from SkCustomTypeface
>
> We added it here https://review.skia.org/540736 but ended up not
> using it for Skottie (only paths). This will help reduce the attack
> surface of deserializing fonts.
>
> Change-Id: Id890c3d0f56f11377563f795f9bfede5a7d84d66
> Bug: 513820666
> Fixed: 513820666
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1245976
> Reviewed-by: Alexis Cruz-Ayala <alexisdavidc@google.com>
> Auto-Submit: Kaylee Lubick <kjlubick@google.com>
> Commit-Queue: Kaylee Lubick <kjlubick@google.com>
> Commit-Queue: Alexis Cruz-Ayala <alexisdavidc@google.com>

(cherry picked from commit 9da67e212e59fbe4f144a92315ca6f8b876c9c01)

Bug: 543625464,513820666,513820666
Change-Id: Id890c3d0f56f11377563f795f9bfede5a7d84d66
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1332776
Auto-Submit: Chrome Cherry Picker <chrome-cherry-picker@chops-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Alexis Cruz-Ayala <alexisdavidc@google.com>
Reviewed-by: Kaylee Lubick <kjlubick@google.com>
Reviewed-by: Alexis Cruz-Ayala <alexisdavidc@google.com>