remove some dead flags

SK_SUPPORT_LEGACY_PAINT_TEXTDECORATION
SK_SUPPORT_LEGACY_DASH_CULL_PATH
SK_SUPPORT_LEGACY_DELTA_AA

Bug: skia:
Change-Id: Id4e2c04936ec8c6887b55d3058e90c4e0508b8a1
Reviewed-on: https://skia-review.googlesource.com/c/159242
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Mike Reed <reed@google.com>
3 files changed