pgsql: Update comment in ExecInsert() regarding batch insertion.

Update comment in ExecInsert() regarding batch insertion.

Remove the stale text that is a leftover from an earlier version of the
patch to add support for batch insertion, and adjust the wording in the
remaining text.

Back-patch to v14 where batch insertion came in.

Review and wording adjustment by Tom Lane.

Discussion: /messages/by-id/CAPmGK14goatHPHQv2Aeu_UTKqZ+BO+P+zd3HKv5D+dyyfWKDSw@mail.gmail.com

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/fc9eb3f0c382dee11099ff400ff29f4b0132f16b

Modified Files
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src/backend/executor/nodeModifyTable.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)