Documentation: RISC-V: Fix a typo in patch-acceptance

I just stumbled on this when modifying the docs.

Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20221207020815.16214-2-palmer@rivosinc.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>