[js-api] `WebAssembly.Exception.getArg()`: missing tag parameter?

[woess]

In the current js-api (v2) spec draft, the getArg method on WebAssembly.Exception is defined asgetArg(unsigned long index), not requiring a tag:

spec/document/js-api/index.bs

Line 1686 in 1d3e26f

any getArg([EnforceRange] unsigned long index);

spec/document/js-api/index.bs

Lines 1754 to 1765 in 1d3e26f

	The <dfn method for="Exception">getArg(|index|)</dfn> method steps are:
	1. Let |store| be the [=surrounding agent=]'s [=associated store=].
	1. Let |tagaddr| be [=exn_tag=](|store|, **this**.\[[Address]]).
	1. Let |payload| be [=exn_read=](|store|, **this**.\[[Address]]).
	1. Assert: |tagaddr| is equal to **this**.\[[Type]].
	1. If |index| ≥ |payload|'s [=list/size=],
	1. Throw a {{RangeError}}.
	1. Let [|types|] → [] be [=tag_type=](|store|, |tagaddr|).
	1. If |types|[|index|] [=matches/valtype|matches=] [=v128=] or [=exnref=],
	1. Throw a {{TypeError}}.
	1. Return [=ToJSValue=](|payload|[|index|]).

This does not align with the description in Exceptions.md and current browser implementations that expect a Tag argument:

spec/proposals/exception-handling/Exceptions.md

Line 279 in 1d3e26f

any getArg(Tag tag, unsigned long index);

spec/proposals/exception-handling/Exceptions.md

Lines 236 to 237 in 1d3e26f

	to query if the `Exception` matches a given tag. The `getArg` method allows
	access to the data fields of a `Exception` if a matching tag is given. This last

It's not entirely clear to me if this is a spec bug or an intentional change that has not been adopted in implementations yet. Either way, one of the two documents needs to be fixed.