qt: Drop buggy TableViewLastColumnResizingFixer class

In Qt 5 the last column resizing with dragging its left edge works
out-of-the-box.
The current TableViewLastColumnResizingFixer implementation could put
the last column content out of the view port and confuse a user.

src/qt/receivecoinsdialog.h

@@ -51,14 +51,12 @@ public Q_SLOTS:
 
 private:
     Ui::ReceiveCoinsDialog *ui;
-    GUIUtil::TableViewLastColumnResizingFixer *columnResizingFixer;
     WalletModel *model;
     QMenu *contextMenu;
     const PlatformStyle *platformStyle;
 
     QModelIndex selectedRow();
     void copyColumnToClipboard(int column);
-    virtual void resizeEvent(QResizeEvent *event) override;
 
 private Q_SLOTS:
     void on_receiveButton_clicked();