remove obsolete guards for hinting enum

Bug: skia:
Change-Id: I694c9b4637d3979e7a11e1ff2c4b51acef59d405
Reviewed-on: https://skia-review.googlesource.com/c/169831
Reviewed-by: Mike Reed <reed@google.com>
diff --git a/gn/flutter_defines.gni b/gn/flutter_defines.gni
index c66de21..351de9b 100644
--- a/gn/flutter_defines.gni
+++ b/gn/flutter_defines.gni
@@ -13,8 +13,6 @@
   "SK_DISABLE_DAA",
 
   # API staging
-  "SK_SUPPORT_LEGACY_NONCLASS_HINTINGENUM",
-  "SK_SUPPORT_LEGACY_NESTED_HINTINGENUM",
 
   # Flutter doesn't deserialize anything.
   "SK_DISABLE_READBUFFER",