[BUG]: (MDA Reference App/Pivot Page) Pivot width is not dynamically set using the slider

[scottdurow]

Describe the bug
The slider on the Pivot reference app page should dynamically change the width of the pivot, however, it has no effect

To Reproduce
Steps to reproduce the behavior:

1. Navigate to the PIvot Page in the MDA Reference App
2. Change the slider in the Pivot Item Styles section

Expected behavior
The pivot should dynamically change width demonstrating the items moving in/out of the overflow

[denise-msft]

This has been fixed and will be available in the october release