remove trailing whitespace

doc/Language/classtut.pod6

@@ -624,7 +624,7 @@ C<$o>, which tells us the exact type of C<$o>: in this case C<Programmer>.
 
 C<$o.perl> returns a string that can be executed as Perl code, and
 reproduces the original object C<$o>. While this does not work perfectly in
-all cases, it is very useful for debugging simple objects. 
+all cases, it is very useful for debugging simple objects.
 N<For example closures cannot easily be reproduced this way; if you
 don't know what a closure is don't worry. Also current implementations have
 problems with dumping cyclic data structures this way, but they are expected