html.img: Remove phantom onerror deprecation

[ferdnyc]

Summary

This PR removes the deprecation annotation from the onerror attribute of the HTML img tag's browser compatibility data.

Test results and supporting details

• mdn/sprints#4014 (including attempts to query @teoli2003, author of Add browser compat info for HTML media elements #388)
• Stackoverflow discussion
• Changes made to update the api.HtmlImageElement reference regarding error-handling, in Fixes to api.HTMLImageElement #4724

Original source of existing data

• Add browser compat info for HTML media elements #388

Related issues

Commit message body

The onerror attribute to the img element has been marked deprecated since the table data was introduced in 061483a. However, that deprecation was never sourced to any specs or references, and multiple inquiries since have failed to uncover any explanation for it. It appears to have been a simple error.

[teoli2003]

I think the current rule is not to list onXYZ content attribute (and so the whole entry should be removed).

Let's double-check this with @queengooborg or @Elchi3.

[queengooborg]

Actually, the rule is not to document event handler attributes on the interface, not the HTML attribute. For the most part, I think we've been keeping the HTML attributes for event handlers?

[ferdnyc]

Another data point:

onerror is discussed in § Image Loading Errors of the MDN article on the <img> element (to which the compatibility chart built from this data is attached), with no mention made of any deprecation.

This is in contrast to every other attribute marked as deprecated in the chart data, which are all gathered together in § Deprecated Attributes of the article.

[teoli2003]

Actually, the rule is not to document event handler attributes on the interface, not the HTML attribute. For the most part, I think we've been keeping the HTML attributes for event handlers?

In that case, we have 100s of "onXYZ" missing on elements. For example, onclick works on the <img> element (even if it is not recommended).

[ferdnyc]

@teoli2003

In that case, we have 100s of "onXYZ" missing on elements. For example, onclick works on the <img> element (even if it is not recommended).

It's possible the idea was that the compatibility chart should provide information on whatever's discussed in the article. Like I said, onerror is mentioned in the error-handling section, none of the other event triggers are.

Personally it doesn't matter to me whether it gets removed or fixed. I just want to stop claiming it's deprecated when it's not.

[Elchi3]

I don't think it is useful to have all the event handlers in the HTML compat data, so this data might get removed, but for now the PR is correct as it stands. The onerror event handler is not deprecated.

[skyclouds2001]

I searched in the repo, and it seems that this is the only event handler property listed in the html part of the BCD