v11 | Notifications action prop and rich text are being deprecated

[dakahn]

For screen reader accessibility notifications cannot contain interactive content or rich text due to limitations with how aria-live and role="alert" are interpreted by screen readers

• content of role="alert" is read as a string, so rich text (headings, emphasis etc) are lost and not accessible
• interactive elements (buttons, links etc) are inaccessible via keyboard and screen reader since notifications do not steal focus

[tay1orjones]

Related #8560