Disable auto-testing of TB2 tests on Chrome

Chrome has started auto-updating even though auto updates are
disabled on the test machines. TestBench 2 works with Chrome 41 (latest)
but opens the test in a new tab instead of in a new window and therefore
is unable to resize the browser to the correct size for screenshots.

Change-Id: Ib7f05a9115a9c82f5b3b384d73c47d6becbfbe79

uitest/test.xml

@@ -7,7 +7,7 @@
     <!-- Configuration -->
     <!-- ================================================================== -->
     <!-- Browsers to use for testing -->
-    <property name="browsers-windows" value="winxp-ie8,win7-ie9,win7-ie10,winxp-firefox17-esr,winxp-googlechrome21" />
+    <property name="browsers-windows" value="winxp-ie8,win7-ie9,win7-ie10,winxp-firefox17-esr" />
     <property name="browsers-linux" value="linux-firefox3,linux-opera10,linux-googlechrome8" />
     <property name="browsers-mac" value="osx-firefox3,osx-opera10,osx-googlechrome8,osx-safari4,osx-safari5" />