Fix typo in README.md

`asf-branch` -> `asf-site` branch
diff --git a/README.md b/README.md
index 89f3cca..cc0c8be 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,7 @@
 and so has been checked out as an orphan branch with its own commit history apart from the master branch. See the *Contributing* section below.
 
 Through a [gitpubsub](http://www.apache.org/dev/gitpubsub.html) mechanism on the apache.org server,
-files are taken from the `asf-branch` and pushed to the live server.
+files are taken from the `asf-site` branch and pushed to the live server.
 
 Pages
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