fix(Felamimail): fix spam info dialog title translation

Change-Id: I0ba0fd42ba24ab80d6720a5a09df66837d515662
Reviewed-on: http://gerrit.tine20.com/customers/18639
Tested-by: Jenkins CI (http://ci.tine20.com/) <tine20-jenkins@metaways.de>
Reviewed-by: Philipp Schüle <p.schuele@metaways.de>

tine20/Felamimail/js/MailDetailsPanel.js

@@ -607,7 +607,7 @@ Ext.extend(Tine.Felamimail.MailDetailsPanel, Ext.Panel, {
                         iconCls: 'action_about',
                         handler: () => {
                             Ext.Msg.alert(
-                                i18n._('Confirm SPAM Suspicion'),
+                                this.app.i18n._('Confirm SPAM Suspicion'),
                                 Tine.Tinebase.configManager.get('spamInfoDialogContent', 'Felamimail')
                             );
                         }