Remove warning for `summary` button role

[leekeh]

There is currently a warning in the specifications for the summary element:

Note

Many, but not all, user agents expose the summary element with an implicit ARIA role=button.

I think this comment is outdated, and related to the fact that the old role of this element is button, which was changed in these PRs:

• Editorial: clarify summary element role mapping #434
• Correction: conditionally revise allowed attributes and roles on summary element #435

I tested the implementation of Firefox, Safari and a Chromium browser and they all did not have any role. So that makes me think that this warning is outdated.

[scottaohara]

thanks for the issue.

for a time it'd probably be better to indicate that user agents used to expose the element as a button. i'm glad that they don't anymore (though that likely creates some different UX issues... and it'd still be interesting to know whether AT still exposes the element as a button or not).

definitely will take care of this in the spec, but likely with another PR. Further testing will also need to be done to make sure that HTML AAM is also in alignment with reality - https://w3c.github.io/html-aam/#el-summary