Fix outdated URLs for element and attribute specs

[melanierichards]

Looks like the URL structure for the HTML5 spec changed; made updates to some URLs here so that they don't just land on the index of that entire spec. Note, I couldn't find a suitable URL for scoped styles or the iframe[seamless] attribute in the editor's draft of the W3C spec.

@jacobrossi @dstorey @kypflug

[msftclas]

@melanierichards,
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[alrra]

Thanks, @melanierichards! 💜

[alrra]

Note, I couldn't find a suitable URL for scoped styles or the iframe[seamless] attribute in the editor's draft of the W3C spec.

@melanierichards That's because they have been removed from the spec(s):

• Remove seamless attribute from iframe w3c/html#325
• Remove scoped style w3c/html#318

[alrra]

couldn't find a suitable URL for scoped styles or the iframe[seamless] attribute in the editor's draft of the W3C spec.

Fixed in b5940c5.