use scan-not-hidden

From-SVN: r183454

gcc/testsuite/g++.dg/ext/visibility/template9.C

 // PR c++/51813
 // { dg-require-visibility "" }
 // { dg-options -fvisibility=hidden }
-// { dg-final { scan-assembler-not "hidden\\s+_ZN1N1fI1AEEvT" } }
+// { dg-final { scan-not-hidden "_ZN1N1fI1AEEvT" } }
 
 struct A { };
 namespace N __attribute((visibility("default"))) {