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

doc/src/sgml/config.sgml

@@ -7684,8 +7684,8 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         which lets modules such as <xref linkend="pgstatstatements"/>
         automatically enable it, and <literal>regress</literal> which
         has the same effect as <literal>auto</literal>, except that the
-        query identifier is hidden in the <literal>EXPLAIN</literal> output
-        to facilitate automated regression testing.
+        query identifier is not shown in the <literal>EXPLAIN</literal> output
+        in order to facilitate automated regression testing.
         The default is <literal>auto</literal>.
        </para>
        <note>