Doc: Remove Ubuntu 14.04, Ubuntu Touch from Supported Platforms

Ubuntu 14.04 (64-bit) is no longer part of the CI. Also remove the
last mention of Ubuntu Touch.

Change-Id: I6bd480aa4a18c882f5528d3fd3c43aed0a1e4ceb
Reviewed-by: Heikki Halmet <heikki.halmet@qt.io>

doc/src/platforms/supported-platforms.qdocinc

@@ -76,9 +76,6 @@ Mobile Platforms: \l {Qt for Android}{Android},
     \row \li Red Hat Enterprise Linux 7.2 (64-bit)
          \li \b {GCC 5.3.1}
          \li devtoolset-4
-    \row \li Ubuntu 14.04 (64-bit)
-         \li GCC 4.8.2
-         \li Ubuntu 4.8.2-19ubuntu1
     \row \li Ubuntu 16.04 (64-bit)
          \li \b {GCC as provided by Canonical}
          \li
@@ -101,7 +98,7 @@ Mobile Platforms: \l {Qt for Android}{Android},
 
     \row \li {3,1} \header \li {3,1}
           Mobile Platforms: \l {Qt for Android}{Android}, \l {Qt for iOS}{iOS},
-          Ubuntu Touch, Universal Windows Platform (UWP)
+          Universal Windows Platform (UWP)
     \row \li Universal Windows Platform (UWP) (x86, \b x86_64, armv7)
          \li \b {MSVC 2017}, \b {MSVC 2015}
          \li Hosts: \b {Windows 10}