TimeSpanHighlight doc: wrong text for clearExisting option of higlightTimeSpans()

[Jerther]

Hello!

Here: https://www.bryntum.com/docs/gantt/api/SchedulerPro/feature/TimeSpanHighlight#function-highlightTimeSpan

Expand the method documentation, and see the text for the clearExisting option. I believe it's inacurrate

[mats]

Fixed, thanks for the heads up