Remove last of SK_SUPPORT_LEGACY_IMAGE_ENCODER_CLASS

Approval from https://review.skia.org/5006
TBR=reed@google.com
Change-Id: Icdd54be420260ecd2f94f2f1fa76caba34e6a50e
Reviewed-on: https://skia-review.googlesource.com/6840
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
2 files changed