Android: Remove MinGW from list of of required downloads

MinGW should be a dependency of the binary installer, there's no need to
download it separately in advance.

Change-Id: I9243cd4087aa626a3fa7fb227aad70478a9fae54
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

doc/src/platforms/android.qdoc

@@ -143,7 +143,6 @@ In order to use \l{Qt for Android}, you need the following:
 \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 On Windows, you need the following additional installations:
   \list
-    \li MinGW v4.8.0 revision 2
     \li Android Debug Bridge (ADB) driver on the Windows platform to enable USB
         debugging. The default USB driver on Windows does not allow debugging.
         For details about how to get the USB driver, see