Documentation: RISC-V: patch-acceptance: s/implementor/implementer

Implementor does appear to be a word, but it's not very common.

Suggested-by: Conor Dooley <conor@kernel.org>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20221207020815.16214-5-palmer@rivosinc.com


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