remove unused code around SK_SUPPORT_LEGACY_XFERMODE_PARAM

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4384

Change-Id: I5121acd027d935ade169ff65941f29f654a47bd0
Reviewed-on: https://skia-review.googlesource.com/4384
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/src/utils/SkLuaCanvas.cpp b/src/utils/SkLuaCanvas.cpp
index 10fc3b4..3949df5 100644
--- a/src/utils/SkLuaCanvas.cpp
+++ b/src/utils/SkLuaCanvas.cpp
@@ -309,7 +309,7 @@
 
 void SkLuaCanvas::onDrawVertices(VertexMode vmode, int vertexCount,
                                  const SkPoint vertices[], const SkPoint texs[],
-                                 const SkColor colors[], SK_XFERMODE_PARAM,
+                                 const SkColor colors[], SkBlendMode,
                                  const uint16_t indices[], int indexCount,
                                  const SkPaint& paint) {
     AUTO_LUA("drawVertices");