Fix WebIDL terms

[momdo]

Per whatwg/webidl@6844bc4 and whatwg/webidl@ad03037 .

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/form-control-infrastructure.html ( diff )
/infrastructure.html ( diff )
/webappapis.html ( diff )

[domenic]

Thanks! However, as you can see from the build error, we need to replace idl-Error.

It seems to appear in

   <li><p>Let <var>errorValue</var> be the value that represents the error: in the case of an
   uncaught exception, that would be the value that was thrown; in the case of a JavaScript error
   that would be an <code data-x="idl-Error">Error</code> object. If there is no corresponding
   value, then the null value must be used instead.</p></li>

which is a known-confusing section that needs a revamp anyway per #958. Maybe just replace it with <code data-x="">Error</code> for now.

[annevk]

The existing usage sites of "convert" also need to be updated to link to the new definition in Infra.

[annevk]

@momdo note that this is still incomplete. The references to the convert term need to be updated as well. Let me know if you'd like help.

[momdo]

@annevk Thanks for replying. For the term convert, could I simply replace it for instance as follows?

Before:

<li><p>Replace <var>name</var> with the result of <span>converting to a sequence of Unicode
   scalar values</span>.</p></li>

After:

<li><p>Replace <var>name</var> with the result of <span>convert</span>.</p></li>

If such a replacement is incorrect, please let me know how to rewrite it.

[annevk]

How about:

Set <var>name</var> to the result of <span data-x="convert">converting</span> <var>name</var>.

[momdo]

@annevk Thank you for comment. Fixed them.

[annevk]

Thanks @momdo!