Fix id attribute on h3 tag for 4.2.x and earlier instructions

The id attribute on the h3 tag for the 4.2.x and earlier instructions was
branch-40x-.... which was the same as for the 4.0.x and earlier instructions.
This patch corrects the tag to be branch-42x-...

Change-Id: I3f498820ed743cafae9dd8a03f14877db48aadfb
diff --git a/src/source/initializing.jd b/src/source/initializing.jd
index 3283575..fdbfbfc 100644
--- a/src/source/initializing.jd
+++ b/src/source/initializing.jd
@@ -251,7 +251,7 @@
 install the Java 6 version of the <a
 href="http://support.apple.com/kb/dl1572">Java JDK</a>.</p>
 
-<h3 id="branch-40x-and-all-earlier-branches">Branch 4.2.x and earlier branches</h3>
+<h3 id="branch-42x-and-all-earlier-branches">Branch 4.2.x and earlier branches</h3>
 <p>To build 4.2.x and earlier source in a Mac OS environment, you will need an Intel/x86
 machine running MacOS 10.6 (Snow Leopard) or MacOS 10.7 (Lion), along with Xcode
 4.2 (Apple's Developer Tools). Although Lion does not come with a JDK, it should