remove dead SK_SUPPORT_LEGACY_IMAGEDESERIALIZER code

Bug: skia:
Change-Id: I76be4b179ff23c8584b62b1bb0fa7a964c2ee97e
Reviewed-on: https://skia-review.googlesource.com/86320
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
6 files changed