pgsql: aio: Minor comment improvements

aio: Minor comment improvements

Reviewed-by: Noah Misch <noah@leadboat.com>
Discussion: /messages/by-id/usbwzckj7q3jhfx3ann3nrfnukmupbs35axvq5zfyeo6nvrzrm@onjhxs2du4st

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/e19dc74491e68e1df05c99c4937929cef3092a3b

Modified Files
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src/backend/storage/smgr/md.c | 2 +-
src/backend/storage/smgr/smgr.c | 8 ++++++++
2 files changed, 9 insertions(+), 1 deletion(-)