databases/py-pgmigrate: Fix version requirement of RUN_DEPENDS

from setup.py:
REQUIREMENTS = [
    'sqlparse >= 0.3.0',
    'psycopg2 >= 2.8.2',
    'PyYAML >= 5.2',
]

Approved by:	portmgr (blanket)
With hat:	python
Reference:	https://github.com/yandex/pgmigrate/blob/1.0.7/setup.py#L33-L37

databases/py-pgmigrate/Makefile

@@ -12,7 +12,7 @@ LICENSE_FILE=	${WRKSRC}/LICENSE
 
 RUN_DEPENDS=	${PYTHON_PKGNAMEPREFIX}psycopg2>=2.8.2:databases/py-psycopg2@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}sqlparse>=0.3.0:databases/py-sqlparse@${PY_FLAVOR} \
-		${PYTHON_PKGNAMEPREFIX}yaml>=5.3.1<6.0:devel/py-yaml@${PY_FLAVOR}
+		${PYTHON_PKGNAMEPREFIX}yaml>=5.2:devel/py-yaml@${PY_FLAVOR}
 
 USES=		python:3.6+
 USE_GITHUB=	yes