pgsql: Fix obsolete references to postgres.h in comments.

Fix obsolete references to postgres.h in comments.

Oversights in commits d08741eab5 and d952373a98.

Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/aMxbfSJ2wLWd32x-%40nathan

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/18cdf5932a279a2c035d44460e1e0cbb659471f2

Modified Files
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src/include/access/htup_details.h | 2 +-
src/include/c.h                   | 2 +-
src/include/utils/expandeddatum.h | 2 +-
src/include/utils/memutils.h      | 2 +-
src/include/utils/varbit.h        | 2 +-
5 files changed, 5 insertions(+), 5 deletions(-)