Editorial: clean up mapping table api references

[scottaohara]

follow on to w3c/aria#2309, and this comment in the switch attribute pr

The remaining api row headers for the mapping tables should either match the other aam specs (just static text of the api name/abbr) or as the 2309 PR does, update to an in-page link to the references section so there can be one consistent link for the APIs, rather than multiple that may need to change to reflect any external URL changes.