Popover has additional border displayed

[zstoyanova9]

Description

Starting from v17.0.0, the Popover component has an additional border displayed around its corners.

Popover appearance before v17.0.0:

Steps To Reproduce

1. Open the following StackBlitz examples and observe the difference in the Popover's appearance:
   • Current appearance - https://stackblitz.com/edit/angular-vw7xa1qy
   • Previous appearance in v16.11.0 - https://stackblitz.com/edit/angular-puxawywp-m6dhtzuz

Actual Behavior

There is an additional border displayed around the corners of the Popover.

Expected Behavior

The additional border should not be displayed.

Workaround

As a possible workaround for achieving the previous appearance, apply custom CSS styling to the Popover as demonstrated in the following StackBlitz example - https://stackblitz.com/edit/angular-vw7xa1qy-cyzq4wrf

Last working version of the Kendo UI for Angular package (if regression).

16.11.0