doc: clarify internal behavior of RECURSIVE CTE queries

Reported-by: Tom Lane

Discussion: https://postgr.es/m/3976627.1662651004@sss.pgh.pa.us

Backpatch-through: 10

Author: bmomjian

doc/src/sgml/queries.sgml

@@ -2173,7 +2173,7 @@ SELECT sum(n) FROM t;
   <note>
    <para>
     While <literal>RECURSIVE</literal> allows queries to be specified
-    recursively, internally all queries are evaluated iteratively.
+    recursively, internally such queries are evaluated iteratively.
    </para>
   </note>