Button icon in SplitButton should be square

[TeyaVes]

Describe the bug The button icon in Kendo SplitButton should be square in the Default theme, currently in Kendo jQuery it is not

To reproduce Steps to reproduce the behavior:

1. Go to https://demos.telerik.com/kendo-ui/toolbar/index
2. Check the Insert Split button

Expected behavior The SplitButton icon should be a square

Screenshots

Affected suites (please remove the unneeded items)

• Kendo UI for jQuery