QSearchField: Remove NSSearchField workaround

This was a workaround for QTBUG-124160.

src/widgets/qsearchfield.h

@@ -5,9 +5,6 @@
 #include <QPointer>
 #include <QMenu>
 
-class QShowEvent;
-class QCloseEvent;
-
 class QSearchFieldPrivate;
 class QSearchField : public QWidget {
   Q_OBJECT
@@ -41,7 +38,6 @@ class QSearchField : public QWidget {
   void returnPressed();
 
  protected:
-  void showEvent(QShowEvent *e) override;
   void resizeEvent(QResizeEvent*) override;
   bool eventFilter(QObject*, QEvent*) override;