Remove mention of Apache Ant from Android documentation

This no longer applies and has not for a while. Gradle is now used, and
included automatically.

Change-Id: Ic9c85329d75383b8dbf997a968f53a314f48c1e7
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

doc/src/platforms/android.qdoc

@@ -151,7 +151,6 @@ In order to use \l{Qt for Android}, you need the following:
 \li \l{http://developer.android.com/tools/sdk/ndk/index.html}{The Android NDK}
     (recommended version 10e)
 \li \l{http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html}{Java SE Development Kit} (JDK) v6 or later. You can also use \l{http://openjdk.java.net}{OpenJDK} on Linux.
-\li \l{http://ant.apache.org/bindownload.cgi}{Apache Ant} v1.8 or later
 \endlist
 
 After installing these tools, update the Android SDK by installing the API