Doc: Remove outdated note about run-time partition pruning

The note is no longer true as of 86dc9005, so remove it.

Author: Amit Langote
Discussion: https://postgr.es/m/CA+HiwqFxQn7Hz1wT+wYgnf_9SK0c4BwOOwFFT8jcSZwJrd8HEA@mail.gmail.com

doc/src/sgml/ddl.sgml

@@ -4678,16 +4678,6 @@ EXPLAIN SELECT count(*) FROM measurement WHERE logdate >= DATE '2008-01-01';
     Partition pruning can be disabled using the
     <xref linkend="guc-enable-partition-pruning"/> setting.
    </para>
-
-   <note>
-    <para>
-     Execution-time partition pruning currently only occurs for the
-     <literal>Append</literal> and <literal>MergeAppend</literal> node types.
-     It is not yet implemented for the <literal>ModifyTable</literal> node
-     type, but that is likely to be changed in a future release of
-     <productname>PostgreSQL</productname>.
-    </para>
-   </note>
   </sect2>
 
   <sect2 id="ddl-partitioning-constraint-exclusion">