Allow pg_monitor to execute pg_current_logfile().

We allow roles with privileges of pg_monitor to execute functions
like pg_ls_logdir(), so it seems natural that such roles would also
be able to execute this function.

Bumps catversion.

Co-authored-by: Pavlo Golub
Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/CAK7ymcLmEYWyQkiCZ64WC-HCzXAB0omM%3DYpj9B3rXe8vUAFMqw%40mail.gmail.com

doc/src/sgml/func.sgml

@@ -23735,6 +23735,11 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
         <xref linkend="guc-log-destination"/>.
         The result reflects the contents of
         the <filename>current_logfiles</filename> file.
+       </para>
+       <para>
+        This function is restricted to superusers and roles with privileges of
+        the <literal>pg_monitor</literal> role by default, but other users can
+        be granted EXECUTE to run the function.
        </para></entry>
       </row>