Fix grammar in error message

John Naylor <john.naylor@postgresql.org>

Commit: 7beda87b6a4e5eae66f06df313581f7f53cab813
Author: John Naylor <john.naylor@postgresql.org>
Date: 2022-09-15T04:40:17Z
Releases: 16.0
Fix grammar in error message

While at it, make ellipses formatting consistent when describing SQL statements.

Ekaterina Kiryanova and Alexander Lakhin

Reviewed by myself and Álvaro Herrera
Discussion: https://www.postgresql.org/message-id/eed5cec0-a542-53da-6a5e-7789c6ed9817%40postgrespro.ru
Backpatch only the grammar fix to v15

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