qmltest: Remove obsolete skipAll function.

The skipAll function has been left in qmltest for a transitional period
to give upstream projects time to catch up with the removal of the
function from the API.  This transitional period is now finished.

Task-number: QTBUG-21652
Change-Id: I10173ef9a676b804e6cf2e7f6e9a82f7b7b4c078
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>

src/imports/testlib/TestCase.qml

@@ -312,12 +312,6 @@ Item {
         throw new Error("QtQuickTest::skip")
     }
 
-    function skipAll(msg) {
-        msg = "The skipAll function is no longer available. Please update this test by changing skipAll to skip."
-        qtest_results.fail(msg, util.callerFile(), util.callerLine())
-        throw new Error("QtQuickTest::skip")
-    }
-
     function expectFail(tag, msg) {
         if (tag === undefined) {
             warn("tag argument missing from expectFail()")