fix typo in translation override docs

docs/docs/configuration/client.rst

@@ -35,7 +35,7 @@ Additionally, you can override any translation string for any language by adding
 a `data-isso-` attribute that is equal to the translation key (found `here`__) with
 `-text-[lang]` appended to it. So, for example, if you want to override the
 english translation of the `postbox-notification` message, you could add
-`data-isso-postbox-notification-lang-en="Select to be notified of replies to your comment"`
+`data-isso-postbox-notification-text-en="Select to be notified of replies to your comment"`
 
 .. __: https://github.com/posativ/isso/blob/master/isso/js/app/i18n/en.js