correcting import theory of examples

--- a/src/HOL/ex/Quickcheck_Narrowing_Examples.thy	Thu Jun 09 09:07:13 2011 +0200
+++ b/src/HOL/ex/Quickcheck_Narrowing_Examples.thy	Thu Jun 09 10:19:51 2011 +0200
@@ -6,7 +6,7 @@
 header {* Examples for narrowing-based testing  *}
 
 theory Quickcheck_Narrowing_Examples
-imports "~~/src/HOL/Library/Quickcheck_Narrowing"
+imports Main
 begin
 
 subsection {* Minimalistic examples *}