pgsql: Docs: wording improvement for compute_query_id = regress

Docs: wording improvement for compute_query_id = regress

It's more accurate to say that the query identifier is not shown when
compute_query_id = regress rather than to say it is hidden.

This change (ebf6c5249) appeared in v14, so it makes sense to backpatch
this small adjustment to keep the documents consistent between v14 and
master.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20220411020336.GB26620@telsasoft.com
Backpatch-through: 14, where compute_query_id = regress was added

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/ea669b8088380cc0bc7c48ab8581ea5fba1c5b4f

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