change flattenable factory to return sk_sp

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1855733002

Review URL: https://codereview.chromium.org/1855733002
diff --git a/src/effects/SkTableColorFilter.cpp b/src/effects/SkTableColorFilter.cpp
index 4ce0b4b..10b71f8 100644
--- a/src/effects/SkTableColorFilter.cpp
+++ b/src/effects/SkTableColorFilter.cpp
@@ -207,7 +207,7 @@
     buffer.writeByteArray(storage, size);
 }
 
-SkFlattenable* SkTable_ColorFilter::CreateProc(SkReadBuffer& buffer) {
+sk_sp<SkFlattenable> SkTable_ColorFilter::CreateProc(SkReadBuffer& buffer) {
     const int flags = buffer.read32();
     const size_t count = gCountNibBits[flags & 0xF];
     SkASSERT(count <= 4);
@@ -251,7 +251,7 @@
         b = ptr;
         ptr += 256;
     }
-    return SkTableColorFilter::MakeARGB(a, r, g, b).release();
+    return SkTableColorFilter::MakeARGB(a, r, g, b);
 }
 
 bool SkTable_ColorFilter::asComponentTable(SkBitmap* table) const {