[MDCButton] Put pointerStyleProvider API under a respondsToSelector conditional to ensure no crashes for 13.4 beta users.
[MDCButton] Put pointerStyleProvider API under a respondsToSelector conditional to ensure no crashes for 13.4 beta users.

PiperOrigin-RevId: 314486597

material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios