ProjectExplorer: Bring back keyboard shortcut for "Manage Sessions"

It got lost in 2d196bd2a1.

Fixes: QTCREATORBUG-26950
Change-Id: If181e478488aa6732bb17fae4d72196854c396f7
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/projectexplorer/projectexplorer.cpp

@@ -1213,9 +1213,10 @@ bool ProjectExplorerPlugin::initialize(const QStringList &arguments, QString *er
     dd->m_sessionManagerAction = new QAction(tr("&Manage..."), this);
     dd->m_sessionMenu->addAction(dd->m_sessionManagerAction);
     dd->m_sessionMenu->addSeparator();
+    cmd = ActionManager::registerAction(dd->m_sessionManagerAction,
+                                        "ProjectExplorer.ManageSessions");
     cmd->setDefaultKeySequence(QKeySequence());
 
-
     // unload action
     dd->m_unloadAction = new ParameterAction(tr("Close Project"), tr("Close Pro&ject \"%1\""),
                                              ParameterAction::AlwaysEnabled, this);