doc: improve CCM example

Applications should never attempt to use the deciphered message
if authentication fails. In reality, this is usually not a problem
since OpenSSL does not disclose the plaintext in this case, but it
is still a design mistake and can lead to critical security problems
in other cipher modes and implementations.

PR-URL: #27396
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rich Trott <rtrott@gmail.com>

doc/api/crypto.md

@@ -2885,6 +2885,7 @@ try {
   decipher.final();
 } catch (err) {
   console.error('Authentication failed!');
+  return;
 }
 
 console.log(receivedPlaintext);