telepathyClient: Fix a translator comment

Ouch, classy - we are telling translators to use a '24h' time
format for the '12h' time format string.
Luckily, only a handful of translations actually followed the
comment (de,hu,id,is,kk,nb,nl), and most of the corresponding
locales do not support 12-hour format anyway (only is_IS, at
least on Fedora).

js/ui/components/telepathyClient.js

@@ -984,7 +984,7 @@ const ChatNotification = new Lang.Class({
         } else {
             // Show only the time if date is on today
             if(daysAgo < 1){
-                /* Translators: Time in 24h format */
+                /* Translators: Time in 12h format */
                 format = N_("%l\u2236%M %p");
             }
             // Show the word "Yesterday" and time if date is on yesterday