Mk/Uses/python.mk: Remove PY_SPHINX shared macro

This shared macro was necessary to use with flavors and not break ports with
USES=python (all versions).

All ports that depends on Sphinx are using the latest version on tree.

Approved by:	python (with hat)

Mk/Uses/python.mk

@@ -645,11 +645,9 @@ PYNUMPY=	${PYTHON_PKGNAMEPREFIX}numpy>=1.16,1<1.20,1:math/py-numpy@${PY_FLAVOR}
 # Common Python modules that can be needed but only for some versions of Python.
 .if ${PYTHON_REL} < 3500
 PY_PYGMENTS=	${PYTHON_PKGNAMEPREFIX}pygments-25>=2.5.1<3:textproc/py-pygments-25@${PY_FLAVOR}
-PY_SPHINX=	${PYTHON_PKGNAMEPREFIX}sphinx18>=0,1:textproc/py-sphinx18@${PY_FLAVOR}
 .else
 PY_PILLOW=	${PYTHON_PKGNAMEPREFIX}pillow>=7.0.0:graphics/py-pillow@${PY_FLAVOR}
 PY_PYGMENTS=	${PYTHON_PKGNAMEPREFIX}pygments>=2.5.1<3:textproc/py-pygments@${PY_FLAVOR}
-PY_SPHINX=	${PYTHON_PKGNAMEPREFIX}sphinx>=3.0,1:textproc/py-sphinx@${PY_FLAVOR}
 .endif
 
 .if ${PYTHON_REL} < 3400