Make the note clearer

Otherwise people might think that closing anything is not needed at all.
Issue #1561.

Author: AlexDaniel

doc/Type/IO/Handle.pod6

@@ -97,7 +97,8 @@ that your program does not open too many files at the same time, triggering
 exceptions on further C<open> calls.
 
 B<Note (Rakudo versions 2017.09 and after):> Open file handles are
-automatically closed on program exit.
+automatically closed on program exit, but it is still highly
+recommended that you C<close> opened handles explicitly.
 
 =head2 method comb