devel/py-mrkd: Change RUN_DEPENDS from py-mistune to py-mistune0

- Bump PORTREVISION for dependency change

This port is not ready for mistune 2.0.0+ which has different API.

devel/py-mrkd/Makefile

 PORTNAME=	mrkd
 PORTVERSION=	0.2.0
-PORTREVISION=	1
+PORTREVISION=	2
 CATEGORIES=	devel python
 MASTER_SITES=	CHEESESHOP
 PKGNAMEPREFIX=	${PYTHON_PKGNAMEPREFIX}
@@ -16,7 +16,7 @@ BUILD_DEPENDS=	${PYTHON_PKGNAMEPREFIX}packaging>=21.3:devel/py-packaging@${PY_FL
 
 RUN_DEPENDS=	${BUILD_DEPENDS} \
 		${PYTHON_PKGNAMEPREFIX}Jinja2>=3.0.1:devel/py-Jinja2@${PY_FLAVOR} \
-		${PYTHON_PKGNAMEPREFIX}mistune>=0.8.4:textproc/py-mistune@${PY_FLAVOR} \
+		${PYTHON_PKGNAMEPREFIX}mistune0>=0.8.4:textproc/py-mistune0@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}pygments>=2.7.2:textproc/py-pygments@${PY_FLAVOR}
 
 USES=		python:3.7+