add ~riscv keyword
tatt report: USE tests started on Fri Mar 10 01:03:11 CST 2023 FEATURES=' test' USE='' succeeded for =kde-apps/kgpg-22.12.3 USE='-handbook' succeeded for =kde-apps/kgpg-22.12.3 USE='handbook' succeeded for =kde-apps/kgpg-22.12.3
riscv done all arches done