Update anope.example.conf

Corrected typo on erroneous option value name. `nickserv:registration` only has as options: none, admin, mail. I assume that `mail` is the word that should replace `yes`

data/anope.example.conf

@@ -916,7 +916,7 @@ mail
 	 * If set, this option enables the mail commands in Anope. You may choose
 	 * to disable it if you have no Sendmail-compatible mailer installed. Whilst
 	 * this directive (and entire block) is optional, it is required if
-	 * nickserv:registration is set to yes.
+	 * nickserv:registration is set to mail.
 	 */
 	usemail = yes