doc PG 17 relnotes: add logical replication apply subtrans item

Reported-by: Masahiko Sawada

Discussion: https://postgr.es/m/CAD21AoD5jjB+M+BK5JTis8=W1g8KsS1961FyMqRpj=NBFXrJeA@mail.gmail.com

Backpatch-through: master

doc/src/sgml/release-17.sgml

@@ -1150,6 +1150,17 @@ Previously only btree indexes could be used for this purpose.
 </para>
 </listitem>
 
+<!--
+Author: Masahiko Sawada <msawada@postgresql.org>
+2024-04-03 [5bec1d6bc] Improve eviction algorithm in ReorderBuffer using max-he
+-->
+
+<listitem>
+<para>
+Improve logical decoding performance in cases where there are many subtransactions (Masahiko Sawada)
+</para>
+</listitem>
+
 <!--
 Author: Amit Kapila <akapila@postgresql.org>
 2023-10-17 [79243de13] Restart the apply worker if the privileges have been rev