When ConcatPair was updated to use || this lost the implicit wrapping from CONCAT(...).
This broke the WHERE clauses when used in combination with PostgreSQL trigram similarity.
Regression in 6364b6ee1071381eb3a23ba6b821fc0d6f0fce75.
Backport of c3ca6075cc0ad425bcf905fe14062f38eb9fbcbf from main.
Co-authored-by: Emiliano Cuenca <106986074+emicuencac@users.noreply.github.com>