locking/seqlock: Fix grammar in comment

The "neither writes before and after ..." for the description
of do_write_seqcount_end() should be "neither writes before nor after".

Signed-off-by: Cuda-Chen <clh960524@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231017053703.11312-1-clh960524@gmail.com