multimedia/mkvtoolnix: Update to upstream version 81.0

Details:
- New features and bugfixes, see
  https://mkvtoolnix.download/doc/NEWS.md

multimedia/mkvtoolnix/Makefile

@@ -1,5 +1,5 @@
 PORTNAME=	mkvtoolnix
-PORTVERSION=	80.0
+PORTVERSION=	81.0
 CATEGORIES=	multimedia audio
 MASTER_SITES=	https://www.bunkus.org/videotools/mkvtoolnix/sources/ \
 		https://mkvtoolnix.download/sources/
@@ -19,7 +19,7 @@ BUILD_DEPENDS=	rake:devel/rubygem-rake \
 LIB_DEPENDS=	libvorbis.so:audio/libvorbis \
 		libogg.so:audio/libogg \
 		libebml.so:textproc/libebml \
-		libboost_regex.so:devel/boost-libs \
+		libboost_system.so:devel/boost-libs \
 		libpugixml.so:textproc/pugixml \
 		libmatroska.so:multimedia/libmatroska \
 		libcmark.so:textproc/cmark \

multimedia/mkvtoolnix/distinfo

@@ -1,3 +1,3 @@
-TIMESTAMP = 1698660719
-SHA256 (mkvtoolnix-80.0.tar.xz) = bb08cdaf9afd472738b9655ae5704c3749da0a51a188baab12f5d7c3eb4d33f5
-SIZE (mkvtoolnix-80.0.tar.xz) = 11056764
+TIMESTAMP = 1702796228
+SHA256 (mkvtoolnix-81.0.tar.xz) = 422f2bec88d5d93547df0c3e1399272a6dc4c23050b45d34343bbdd6d55e5ad6
+SIZE (mkvtoolnix-81.0.tar.xz) = 11067288