Remove duplicate word; closes #1371

Author: zoffixznet

doc/Type/Failure.pod6

@@ -63,7 +63,7 @@ Defined as:
     method exception(Failure:D: --> Failure:D)
 
 If the invocant is a L<handled> C<Failure>, returns it as is.
-If not not handled, throws its L<Exception>. Since
+If not handled, throws its L<Exception>. Since
 L<Mu> type L«provides C<.self>|/type/Mu#method_self» for every
 class, calling this method is a handy way to explosively
 filter out Failures: