release notes: move pg_buffercache item to the right section

Report by Amit Langote

doc/src/sgml/release-9.5.sgml

@@ -1858,6 +1858,13 @@
       </para>
      </listitem>
 
+     <listitem>
+      <para>
+       Add information about buffer pins to <application>pg_buffercache</>
+       display (Andres Freund)
+      </para>
+     </listitem>
+
      <listitem>
       <para>
        Allow <application>pgstattuple</> to report approximate answers
@@ -1914,13 +1921,6 @@
        </para>
       </listitem>
 
-      <listitem>
-       <para>
-        Add information about buffer pins to <application>pg_buffercache</>
-        display (Andres Freund)
-       </para>
-      </listitem>
-
       <listitem>
        <para>
         Allow <application>pgbench</>'s <command>\set</> command to handle