[S06] fix a logic flaw introduced in 15f0b2b

Author: moritz

S06-routines.pod

@@ -2648,7 +2648,7 @@ their own C<.TEMP> methods:
     class LoudArray is Array {
         method TEMP {
             print "Replacing $.WHICH() at {caller.location}\n";
-            my $restorer = callsame;
+            my $restorer = nextsame;
             return {
                 print "Restoring $.WHICH() at {caller.location}\n";
                 $restorer();