remove obsolete flags from public.bzl

BUG=skia:
NOTRY=True

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4495

Change-Id: I79635fee732135a1ac33aceee30e5f2d4aa08ac2
Reviewed-on: https://skia-review.googlesource.com/4495
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>
diff --git a/public.bzl b/public.bzl
index f2ed85e..de3d6f2 100644
--- a/public.bzl
+++ b/public.bzl
@@ -599,10 +599,8 @@
     # Turn on a few Google3-specific build fixes.
     "GOOGLE3",
     # Staging flags for API changes
-    "SK_SUPPORT_LEGACY_XFERMODE_PARAM_TYPES",
     "SK_SUPPORT_LEGACY_ACCESSBITMAP",
     "SK_SUPPORT_LEGACY_CLIP_REGIONOPS",
-    "SK_SUPPORT_LEGACY_SETIMAGEFILTER_PTR",
 ]
 
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