Remove deadcode ; delete keypress will never reach DockBookmark

 Notice that eventFilter is attached to ui->tableViewFrequencyList that
 is only the frame border of the QTableView. To properly work it should
 be attached to ui->tableViewFrequencyList->viewport().

 In any case here, delete key press will be preempted by QShortcut
 defined in MainWindow class to clear the waterfall.

src/qtgui/dockbookmarks.cpp

@@ -159,14 +159,6 @@ bool DockBookmarks::eventFilter(QObject* object, QEvent* event)
     {
         ui->tableViewFrequencyList->clearSelection();
     }
-    if (event->type() == QEvent::KeyPress)
-    {
-        QKeyEvent* pKeyEvent = static_cast<QKeyEvent *>(event);
-        if (pKeyEvent->key() == Qt::Key_Delete && ui->tableViewFrequencyList->hasFocus())
-        {
-            return DeleteSelectedBookmark();
-        }
-    }
     return false;
 }