Do not mark abstract operations with `data-export`

[saschanaz]

What is the issue with the Streams Standard?

Those are intended to be internal and should not be marked as data-export. But things like https://streams.spec.whatwg.org/#readable-stream-cancel gets:

<dfn class="dfn-paneled has-dfn-panel" data-dfn-type="abstract-op" data-export="" data-lt="ReadableStreamCancel" id="readable-stream-cancel" role="button" aria-expanded="true" tabindex="100">ReadableStreamCancel(<var>stream</var>, <var>reason</var>)<button class="specmonkey-box-button"><img src="moz-extension://19959b45-e51e-4132-a315-badf5b67dba2/searchfox.png" alt="SpecMonkey" class="specmonkey-box-icon"></button></dfn>

Not quite sure where the data-export is coming from, it's not in the source:

streams/index.bs

Lines 2711 to 2712 in 7611362

	<dfn abstract-op lt="ReadableStreamCancel"
	id="readable-stream-cancel">ReadableStreamCancel(|stream|, |reason|)</dfn> performs the following

Perhaps the explicit ID is somehow making it exported?

[saschanaz]

https://speced.github.io/bikeshed/#dfn-contract

If neither is provided, "dfn" type definitions default to noexport, while all others default to export. Unexported definitions aren’t linkable by default.

I guess abstract-op made it exported.