Update README.fuchsia to specify upstream branch.
diff --git a/README.fuchsia b/README.fuchsia
index bf93f45..5d70ae2 100644
@@ -11,6 +11,7 @@
Contains support for applying an ICC color profile to an image. The code is
originally based on tinycms, re-written by Mozilla for better security and
performance. This copy is a source-drop from Mozilla on March 13, 2012.
+This branch is based off of upstream/v4.
Some files only have license headers in the master branch.