Fix incorrect size given to bqueue_enqueue() call in dmu_redact.c

We pass sizeof (struct redact_record *) rather than sizeof (struct
redact_record). Passing the pointer size is wrong.

Coverity caught this in two places.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #13885