Accessibility fixes to dynamic tabs (`aria-selected`, remove dynamic tabs with dropdowns) (!23907) · Merge requests · Bootstrap / bootstrap

Fixes our current incorrect use of aria-expanded rather than the proper aria-selected (see https://www.w3.org/TR/wai-aria-practices/#tabpanel)
Removes dynamic tabbed interfaces with dropdowns, as they're not good for usability and more importantly not a pattern that can be expressed/conveyed to assistive tech