### Is this a regression? - [ ] Yes, this behavior used to work in the previous version ### The previous version in which this bug was not present was _No response_ ### Description WAVE tool reports the accessibility error (WCAG A) as "Empty table header" to datepicker calendar popup views (month, year, multi-year). An empty <th> for the divider causes the error.  ### Reproduction Steps to reproduce: To replicate the issue, 1. go to Datepicker examples page: https://material.angular.io/components/datepicker/overview 2. click a calendar icon to popup the calendar view. Then open WAVE extension.   ### Expected Behavior in <th>, use a hidden text to describe the divider. ### Actual Behavior To replicate the issue, go to Datepicker examples page, click a calendar icon to popup the calendar view. Then open WAVE extension. https://material.angular.io/components/datepicker/overview ### Environment - Angular: - CDK/Material: - Browser(s): - Operating System (e.g. Windows, macOS, Ubuntu):