textproc/py-sphinx18: Mark as deprecated and set an expiry date

Sphinx 1.8.5 was necessary for Python 2, all ports now are using the latest
Sphinx version on tree.

Approved by:	python (with hat)

textproc/py-sphinx18/Makefile

@@ -21,6 +21,9 @@ COMMENT=	Python documentation generator
 LICENSE=	BSD2CLAUSE
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
+DEPRECATED=	Old version, use textproc/py-sphinx instead
+EXPIRATION_DATE=2021-02-15
+
 BUILD_DEPENDS=	${PYTHON_PKGNAMEPREFIX}Jinja2>=2.3:devel/py-Jinja2@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}docutils>=0.11:textproc/py-docutils@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}six>=1.5:devel/py-six@${PY_FLAVOR}