remove dead code from SK_SUPPORT_LEGACY_THREADED_DAA_BUGS

No one sets this flag anymore

Bug: skia:
Change-Id: Icda651823fc8aeeb58cb0865ada32aa50190db58
Reviewed-on: https://skia-review.googlesource.com/c/162023
Commit-Queue: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
2 files changed