testing/kicad: enable kicad-opencascade for all supported archs

Only riscv64 and s390x do not have opencascade and vtk, so they are the only archs that cannot provide kicad-opencacade. However, both are also currently unsupported anyway. Still, the code to only provide "vanilla KiCad" (without support for STEP files) for those archs is left in place, in the hope that at least this version will get support.