textproc/py-xmlschema: Update to 1.8.1

Changelog:	https://github.com/sissaschool/xmlschema/blob/v1.8.1/CHANGELOG.rst

textproc/py-xmlschema/Makefile

 PORTNAME=	xmlschema
-DISTVERSION=	1.8.0
+DISTVERSION=	1.8.1
 CATEGORIES=	textproc python
 MASTER_SITES=	CHEESESHOP
 PKGNAMEPREFIX=	${PYTHON_PKGNAMEPREFIX}

textproc/py-xmlschema/distinfo

-TIMESTAMP = 1633173504
-SHA256 (xmlschema-1.8.0.tar.gz) = fa4e22a708f08d15f605c9191e2500149ba1a848fff7fa4904c2f2c57dc1087f
-SIZE (xmlschema-1.8.0.tar.gz) = 379305
+TIMESTAMP = 1634947646
+SHA256 (xmlschema-1.8.1.tar.gz) = 8b3c2d1f8fab8c3ea021fb66e24504c301fb024aa7aa3ed90aa36cea6f71b625
+SIZE (xmlschema-1.8.1.tar.gz) = 390835