Fixup license name

Libs/Widgets/ctkPopupWidget_p.h

@@ -8,7 +8,7 @@
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at
 
-      http://www.commontk.org/LICENSE
+      http://www.apache.org/licenses/LICENSE-2.0.txt
 
   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,