Bug Description

When you add a filter to a column on the spreadsheet component, only the down arrow icon part of the filter button is clickable, not the entire button.

Steps to Reproduce

1. Open the Dojo - https://dojo.telerik.com/dmrXJIdC
2. Try to click on the filter buttons (.k-spreadsheet-filter)

Expected Behavior

The filter menu is not opened unless we click on the icon.

Actual Behavior

The filter menu should open when the button is clicked.