RFC 6265 "HTTP State Management Mechanism" defines the syntax for Cookies here: https://httpwg.org/specs/rfc6265.html#rfc.section.4.1.1

According to this syntax, a trailing semicolon is not allowed.

I did not experiment how browsers (or more general: User Agents) treat this violation of the official syntax, but in case you implement a service, I would not rely on that behavior anyway and would strongly recommend sticking to the syntax as defined.