CI: use amd64 EDK II firmware included with QEMU

QEMU (now) includes a prebuilt EDK II firmare in edk2-x86_64-code.fd.
Use that instead of requring a standalone uefi-edk2-qemu-x86_64 package.

Reviewed by: imp
MFC after: 3 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D30915

(cherry picked from commit 7d9794b34bcd465a380f05b02ccfea469dd0a48e)