doc PG 17 relnotes: improve text for pg_walfile_name*()

Reported-by: Yugo Nagata

Discussion: https://postgr.es/m/20240726132224.3a77e79c4e563125c451e865@sraoss.co.jp

Backpatch-through: 17 only

Author: bmomjian

doc/src/sgml/release-17.sgml

@@ -176,7 +176,7 @@ Author: Bruce Momjian <bruce@momjian.us>
      and <function>pg_walfile_name_offset()</function> used to report
      the previous <acronym>LSN</acronym> segment number when the
      <acronym>LSN</acronym> was on a file segment boundary;  it now
-     returns the <acronym>LSN</acronym> segment.
+     returns the current <acronym>LSN</acronym> segment.
      </para>
     </listitem>