Doc: corrected description of QTableWidget::clear()

Task-number: QTBUG-36329
Change-Id: I3a78311bcb076b414ecf1ecf866e4ed60c391126
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>

src/widgets/itemviews/qtablewidget.cpp

@@ -2515,7 +2515,9 @@ void QTableWidget::removeColumn(int column)
 
 /*!
    Removes all items in the view.
-   This will also remove all selections.
+   This will also remove all selections and headers.
+   If you don't want to remove the headers, use
+   QTableWidget::clearContents().
    The table dimensions stay the same.
 */