Update contexts.pod6

bad link fix

Author: finanalyst

doc/Language/contexts.pod6

@@ -80,7 +80,7 @@ say True+$list; # OUTPUT: «4␤»
 =end code
 
 In the case of I<listy> things, the numeric value will be in general equivalent
-to C<.elems>; in some cases, like L<Thread|/Numeric#(Thread)_method_Numeric> it
+to C<.elems>; in some cases, like L<Thread|/routine/Numeric#(Thread)_method_Numeric> it
 will return an unique thread identifier.
 
 =head1 String X<|string context>