pgsql: Decorate WITH with literal markup tags

Decorate WITH with literal markup tags

One instance of "WITH clause" was not using <literal> tags around
WITH, while others were, so add markup to the last one to ensure
consistency.  Backpatch to v15 where MERGE was added.

Reported-by: jian he <jian.universality@gmail.com>
Discussion: https://postgr.es/m/CACJufxGJKY9ZCPV2WDM6xFsXq9C8r7r3vU6AkScN+p9k6CEpMw@mail.gmail.com
Backpatch-through: v15

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/25e5663b8cd3a63008b9bea790d9a41e569103fe

Modified Files
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doc/src/sgml/ref/merge.sgml | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)