The blacking out of a JP's name and signature is immaterial to the validity of the search warrant as admissible evidence, specifically because it is only blocked out on the copy given to the recipient. Provided the JP who endorsed the search warrant can present to the Court on request and confirm they have met their obligations when they endorsed the search warrant, that's the extent of their role in ensuring the search warrant is admissible as evidence. The blacking out of their registration number, signature and name is to protect their identity.
Source: I'm a JP.