textproc/xml2rfc: Update to 3.19.4

See https://github.com/ietf-tools/xml2rfc/releases/tag/v3.19.4 for a
list of changes in this release.

Additionally, update the pkg-message to point to another xml2rfx
reference (thanks to John Levine for the suggestion)..

PR:		276929

textproc/xml2rfc/Makefile

@@ -1,5 +1,5 @@
 PORTNAME=	xml2rfc
-PORTVERSION=	3.19.2
+PORTVERSION=	3.19.4
 CATEGORIES=	textproc
 MASTER_SITES=	PYPI
 PKGNAMEPREFIX=	${PYTHON_PKGNAMEPREFIX}

textproc/xml2rfc/distinfo

@@ -1,3 +1,3 @@
-TIMESTAMP = 1706979198
-SHA256 (xml2rfc-3.19.2.tar.gz) = 6ae3b288ff5e421274eb68291fed1c47f648fc8868a4ac46817376b3e458f92b
-SIZE (xml2rfc-3.19.2.tar.gz) = 2654458
+TIMESTAMP = 1708376531
+SHA256 (xml2rfc-3.19.4.tar.gz) = 29c842a726036277895b420d7c8b813f9c26e9e68fc225abd18e3065f98336b4
+SIZE (xml2rfc-3.19.4.tar.gz) = 2656011

textproc/xml2rfc/pkg-message

@@ -1,8 +1,8 @@
 [
 { type: install
   message: <<EOM
-	Have a look at http://xml.resource.org/ for how to get and
-	update bibliographic summaries of each RFC and Internet-Draft.
+	See https://authors.ietf.org/en/references-in-rfcxml for advice
+	on using the reference library at https://bib.ietf.org/
 EOM
 }
 ]