use another web site for the get w/timestamp tests, www.apache.org does not provide Last-Modified information

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@510750 13f79535-47bb-0310-9956-ffa450edef68

src/etc/testcases/taskdefs/get.xml

@@ -60,7 +60,7 @@
 
     <touch file="get.tmp" datetime="${dt}" pattern="${pat}" />
 
-    <get src="http://www.apache.org/" dest="get.tmp"
+    <get src="http://www.w3.org/MarkUp" dest="get.tmp"
          usetimestamp="true" verbose="true" />
 
     <fileset id="ts" file="get.tmp">