scripted-diff: Remove unused "What's This" button in dialogs on Windows

-BEGIN VERIFY SCRIPT-
git grep -l 'QDialog(parent)' -- src/qt | xargs sed -i -E 's/QDialog\(parent\)/QDialog\(parent, GUIUtil::dialog_flags\)/g'
-END VERIFY SCRIPT-

src/qt/coincontroldialog.cpp

@@ -42,7 +42,7 @@ bool CCoinControlWidgetItem::operator<(const QTreeWidgetItem &other) const {
 }
 
 CoinControlDialog::CoinControlDialog(CCoinControl& coin_control, WalletModel* _model, const PlatformStyle *_platformStyle, QWidget *parent) :
-    QDialog(parent),
+    QDialog(parent, GUIUtil::dialog_flags),
     ui(new Ui::CoinControlDialog),
     m_coin_control(coin_control),
     model(_model),