Shorten room subtitles for direct chats

Direct chats by their very nature is between two users, and you usually
can keep track of who said what. There's no point in including the
sender's name here, and most other chat applications exclude it for this
reason (including Element X.)

src/libneochat/eventhandler.cpp

@@ -697,6 +697,9 @@ QString EventHandler::subtitleText(const NeoChatRoom *room, const Quotient::Room
         qCWarning(EventHandling) << "subtitleText called with event set to nullptr.";
         return {};
     }
+    if (room->isDirectChat()) {
+        return plainBody(room, event, true);
+    }
     return singleLineAuthorDisplayname(room, event) + (event->isStateEvent() ? u" "_s : u": "_s) + plainBody(room, event, true);
 }