Update SkBlurImageFilter to sk_sp

TBR=reed@google.com

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1852743002

Review URL: https://codereview.chromium.org/1852743002
diff --git a/gm/imageblur2.cpp b/gm/imageblur2.cpp
index 2b95c02..c6835d8 100644
--- a/gm/imageblur2.cpp
+++ b/gm/imageblur2.cpp
@@ -58,8 +58,7 @@
                 SkScalar sigmaY = kBlurSigmas[y];
 
                 SkPaint paint;
-                SkAutoTUnref<SkImageFilter> blur(SkBlurImageFilter::Create(sigmaX, sigmaY));
-                paint.setImageFilter(blur);
+                paint.setImageFilter(SkBlurImageFilter::Make(sigmaX, sigmaY, nullptr));
                 canvas->saveLayer(nullptr, &paint);
 
                 SkRandom rand;
@@ -89,7 +88,6 @@
 
 //////////////////////////////////////////////////////////////////////////////
 
-static GM* MyFactory(void*) { return new BlurImageFilter; }
-static GMRegistry reg(MyFactory);
+DEF_GM(return new BlurImageFilter;)
 
 }