Remove/rewrite misleading documentation for accessible tooltips

Our documentation (unwisely) recommends overriding the styles of a Pajamas component as a solution to adding accessible tooltips.

Authors should not override the styles of Pajamas components, for various reasons.

Possible solutions:

• Create a dedicated component for the sole use case of icon-only tooltip controls. This is probably best, as we can require an accessible name for the button.
• Document using a plain button element with the needed utility classes applied.