docs: adjust simpler language for NULL return from ANY/ALL

Adjustment to commit 8610c97.

Reported-by: Tom Lane

Discussion: https://postgr.es/m/17406.1541168421@sss.pgh.pa.us

Backpatch-through: 9.3

Author: bmomjian

doc/src/sgml/func.sgml

@@ -15247,7 +15247,7 @@ WHERE EXISTS (SELECT 1 FROM tab2 WHERE col2 = tab1.col2);
    subquery row (including the case where the subquery returns no
    rows).
    The result is NULL if no comparison with a subquery row returns true,
-   and it returns NULL for at least one row.
+   and at least one comparison returns NULL.
   </para>
 
   <para>
@@ -15273,7 +15273,7 @@ WHERE EXISTS (SELECT 1 FROM tab2 WHERE col2 = tab1.col2);
    (including the case where the subquery returns no rows).
    The result is <quote>false</quote> if any false result is found.
    The result is NULL if no comparison with a subquery row returns false,
-   and it returns NULL for at least one row.
+   and at least one comparison returns NULL.
   </para>
 
   <para>
@@ -15303,7 +15303,7 @@ WHERE EXISTS (SELECT 1 FROM tab2 WHERE col2 = tab1.col2);
    The result is <quote>false</quote> if the comparison returns false for any
    subquery row.
    The result is NULL if no comparison with a subquery row returns false,
-   and it returns NULL for at least one row.
+   and at least one comparison returns NULL.
   </para>
 
   <para>