Removal of the acid test reference

[iherman]

This is the counterpart of w3c/epub-tests#167

[iherman]

(Before I do this change) in line of the recent resolution and the merge of #2330 I believe the bullet item

MUST support the official definition of CSS as described in the [csssnapshot].

should be removed altogether (at the moment it only removes the reference to the acid test). The introduction to the section (the yellow box) is the one which counts. (Maybe that sentence should also get a reference to the snapshot.)

I am happy to amend the PR accordingly, but I would prefer to have some positive nods first...

[iherman]

Actually... aren't the entries

• SHOULD apply EPUB creator style sheets as written to EPUB content documents.
• SHOULD NOT override the EPUB creator's style sheets, but SHOULD do so in a way that preserves the Cascade when necessary: through a user agent style sheet, the getOverrideStyle method [dom-level-2-style], or [html] style attributes.

also to be removed? These are just repeating the way an HTML+CSS user agent work...

[iherman]

@mattgarrish @wareid @dauwhe any comment on #2334 (comment) and #2334 (comment) ?