Final call: Improve examples for button-accessible-name

Hey folks,
Another final call. Fairly small change in the button has accessible name
rule:

- Improve the example descriptions
- Remove any passed / inapplicable examples that do not satisfy the
accessibility requirement
- Clean up an example that was overly complicated.

You can see the changes here:
  https://github.com/act-rules/act-rules.github.io/pull/1028

If you have any concerns, please submit a "changed requested" review before
December 4th.

Kind regards,

-- 
*Wilco Fiers*
Axe for Web product owner - Co-facilitator WCAG-ACT - Chair ACT-R