remove SK_SUPPORT_LEGACY_FONT_FLAGS from flutter

Bug: skia:
Change-Id: I79b85a6b57b2193a5a64798eae3dd44e711dcc12
Reviewed-on: https://skia-review.googlesource.com/c/171526
Reviewed-by: Mike Reed <reed@google.com>
diff --git a/gn/flutter_defines.gni b/gn/flutter_defines.gni
index 33e446b..08c9b53 100644
--- a/gn/flutter_defines.gni
+++ b/gn/flutter_defines.gni
@@ -15,7 +15,6 @@
 
   # API staging
   "SK_SUPPORT_LEGACY_NESTED_HINTINGENUM",
-  "SK_SUPPORT_LEGACY_FONT_FLAGS",
 
   # Flutter doesn't deserialize anything.
   "SK_DISABLE_READBUFFER",