Use sk_sp text blob APIs

SkTextBlobBuilder::build()      -> make()
SkAutoTUnref<const SkTextBlob>  -> sk_sp<SkTextBlob>
drawTextBlob(const SkTextBlob*) -> drawTextBlob(const sk_sp<SkTextBlob>&)

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2335493005

Review-Url: https://codereview.chromium.org/2335493005
diff --git a/gm/textblobcolortrans.cpp b/gm/textblobcolortrans.cpp
index 1e7a666..286dc77 100644
--- a/gm/textblobcolortrans.cpp
+++ b/gm/textblobcolortrans.cpp
@@ -48,7 +48,7 @@
         sk_tool_utils::add_to_text_blob(&builder, text, paint, 0, yOffset - 8);
 
         // build
-        fBlob.reset(builder.build());
+        fBlob = builder.make();
     }
 
     SkString onShortName() override {
@@ -87,7 +87,7 @@
     }
 
 private:
-    SkAutoTUnref<const SkTextBlob> fBlob;
+    sk_sp<SkTextBlob> fBlob;
 
     static constexpr int kWidth = 675;
     static constexpr int kHeight = 1600;