Use code formatting

Author: stoned

doc/Type/Thread.pod6

@@ -14,7 +14,7 @@ system threads).
 
 Since threads are fairly low-level, most applications should use other
 primitives, like L«C<start>|/type/Promise#method_start», which also runs in
-parallel and returns a L<Promise|/type/Promise>.
+parallel and returns a L«C<Promise>|/type/Promise».
 
 =begin code
 my @threads = (^10).map: {