Final call for updates to rule - `iframe` element has non-empty accessible name

Hi All,

This PR - https://github.com/act-rules/act-rules.github.io/pull/1322 involves
updates to the rule - `iframe` element has non-empty accessible name, which
resolves TF feedback as detailed in issue -
https://github.com/w3c/wcag-act/issues/435

The final call is 1 week long and will end on 24th June 2020.

Best
Jey