ProcessManager: Make the toolbar actions work again.

We can't grab at the ProcessTableModel directly anymore since we have a
sorting proxy model in the middle now.

Applications/ProcessManager/ProcessTableView.h

@@ -20,10 +20,5 @@ protected:
 
 private:
     virtual void timer_event(GTimerEvent&) override;
-
-    ProcessTableModel& model() { return *m_model; }
-    const ProcessTableModel& model() const { return *m_model; }
-
-    ProcessTableModel* m_model { nullptr };
 };