Improve sending message with mentions

* Fix bug with reply having broken mentions (@$1:$2)
* Fix mentions disapearing from edited messages
* Fix formatting disapearing from edited messages

src/actionshandler.h

@@ -70,8 +70,7 @@ public Q_SLOTS:
     ///
     /// This also interprets commands if any.
     void postMessage(const QString &text, const QString &attachementPath,
-        const QString &replyEventId, const QString &editEventId,
-        const QVariantMap usernames);
+        const QString &replyEventId, const QString &editEventId);
 
 private:
     Connection *m_connection = nullptr;