remove trailing whitespace

Author: coke

doc/Language/control.pod6

@@ -342,7 +342,7 @@ that case and C<Any> smart matches on C<True>: C<Any ~~ True> yields C<True>).
     my $b = True;
     when $a    { say 'a' }; # no output
     when so $a { say 'a' }  # a (in "so $a" 'so' coerces $a to Boolean context True
-                            # which matches with Any) 
+                            # which matches with Any)
     when $b    { say 'b' }; # b (b is True as defined so matches with Any)
 }
 =end code