I see two parts to balance.
The first is if the retraction means there is no evidence that the claim is widely believed, we should consider it no longer notable.
To give some extreme examples, I think both of these claims would be off-topic:
However, a retraction (or in the case of the example question, quiet editing of the article to throw the claim into the memory hole) may not get as widespread publicity as the original claim, leaving people continuing to believe the claim.
In that case, the question is still notable - many people believe it. It should be reasonably feasible to find more examples of the claim being promulgated by them. Multiple such examples should be plenty to show that the question is still notable even after it has been retracted.
[Disclosure: My question, with 10 up-votes at the time of writing, was given as the example, but given I am arguing it should be closed until it is edited to have more examples, I don't think there is a conflict of interest here.]