No, Unless an Exception is Explicitly Stated
There is no rule about 9-again qualities 'adding up' into 8-again (or other cumulative effects of 9- or 8-again) in the second edition corebook. (There are no provisions for a 7-again in a roll either, if it matters to you.) There are Merits which provide either a 9-again or an 8-again quality depending on level of the Merit (e.g. Trained Observer), but that's not a case of cumulativity.
In general, if one edition has a clause and another doesn't, it's 'unsafe' to just assume that the clause from an older edition applies to the new one. Such assumptions often lead to unforeseen and/or undesirable consequences. Also, one should not assume that the omission was accidental without serious evidence: if a clause is removed between editions, it usually doesn't make sense to spend the word count on explaining that this is intentional.
On exceptions: A common principle of handling the writing and interpretation of rules is that the specific overrides the general. Thus, even though there is no general rule on cumulative effects of 9-again, it's possible for a specific splat ability, equipment item, or the like, to have an explicit exception that states to 'upgrade' the roll quality. If so, this is an exception that overrides the general principle only in this case; do not use it as evidence for how things are handled elsewhere. (It does serve as evidence that an overruling is possible, but given the existence of Rule Zero, that's a borderline useless observation.)