Per paragraph 4 above, 1903 for the Presbyterian Church USA (which is one of three major components in the current PCUSA). The OPC (which is the subject of this article), the PCA, and the EPC never used a version referring to the Pope as the Antichrist. I’d have to research to see the history as to some of the other groups.
More than once the Westminister Confession has been cited in posts on this forum, and those quotes retained the charge that the Pope was the Anti-Christ. Nor was that charge denied or repudiated by the person who offered that selection of the WCF.