Remove staging SkStream::unref().

SkStream::unref() was added to ease transitioning off of SkStream
deriving from SkRefCnt. It is no longer needed, remove it.

TBR=reed@google.com

Review URL: https://codereview.chromium.org/861413002
diff --git a/src/utils/win/SkDWriteFontFileStream.cpp b/src/utils/win/SkDWriteFontFileStream.cpp
index 5569db5..809ae7b 100644
--- a/src/utils/win/SkDWriteFontFileStream.cpp
+++ b/src/utils/win/SkDWriteFontFileStream.cpp
@@ -103,7 +103,7 @@
 }
 
 SkDWriteFontFileStream* SkDWriteFontFileStream::fork() const {
-    SkAutoTUnref<SkDWriteFontFileStream> that(this->duplicate());
+    SkAutoTDelete<SkDWriteFontFileStream> that(this->duplicate());
     that->seek(fPos);
     return that.detach();
 }