Fix consecutive <dd> elements in Web/API

[wbamberg]

This is part of #8474.

This PR fixes <dl> elements which don't convert to Markdown because they contain consecutive <dd> elements. This is allowed in <dl> but not in the version of <dl> we support (https://developer.mozilla.org/en-US/docs/MDN/Contribute/Markdown_in_MDN#definition_lists). In practice, when this happens in our source, it is always (?) an error.

Usually this is a matter of converting <dd>s to <p> elements, but in a couple of places it got a bit more extensive:

• https://github.com/mdn/content/compare/main...wbamberg:fix-consective-dd-api?expand=1#diff-b0eb4660e4265e8b31ac64efb446caf9810e755d3a9954e93312f9142110d87c was a rewrite to be more comprehensible
• https://github.com/mdn/content/compare/main...wbamberg:fix-consective-dd-api?expand=1#diff-039b4c5ecc6a6f87457411ab817d672fb16db813951d6c2b5ed04ad2eb240af3 I deleted the second <dd> as it seemed TMI in that context (landing page)
• https://github.com/mdn/content/compare/main...wbamberg:fix-consective-dd-api?expand=1#diff-4898432e26a8d800cf6546e64926102c060e479f2b0293f0a8cc286eaaa90654 I replaced the {{page}} macro with copy/paste - there's definitely more work to do in this area but I didn't want to get into it here.
• https://github.com/mdn/content/compare/main...wbamberg:fix-consective-dd-api?expand=1#diff-fb05d1d4239bacbaee2620946c51cf6fecba4577b9a29563c5c92c31b598a315 I deleted some long-removed things.