pgsql: Small terminology fixes in comments

Small terminology fixes in comments

Author: jian he <jian.universality@gmail.com>
Discussion: /messages/by-id/CAHg+QDcd=t69gLf9yQexO07EJ2mx0Z70NFHo6h94X1EDA=hM0g@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f0aedc7cb0ed82d4cca48332dc0852c767514558

Modified Files
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src/test/regress/expected/for_portion_of.out | 4 ++--
src/test/regress/sql/for_portion_of.sql | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)