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/sendcoinsdialog.cpp

@@ -53,7 +53,7 @@ int getIndexForConfTarget(int target) {
 }
 
 SendCoinsDialog::SendCoinsDialog(const PlatformStyle *_platformStyle, QWidget *parent) :
-    QDialog(parent),
+    QDialog(parent, GUIUtil::dialog_flags),
     ui(new Ui::SendCoinsDialog),
     clientModel(nullptr),
     model(nullptr),