Doctest added to property not tested

[oscarbenjamin]

This doctest should fail:

sympy/sympy/matrices/matrices.py

Lines 1611 to 1617 in 0fbe6d0

	>>> A = Matrix([[1, 2], [2, 1]])
	>>> A.is_positive_definite
	False
	>>> A.is_positive_semidefinite
	False
	>>> A.is_negative_definite
	True

It does fail under pytest but may be it is ignored by the internal doctest runner.

I think it's because of this:

sympy/sympy/matrices/matrices.py

Lines 1655 to 1656 in 0fbe6d0

	is_negative_definite = \
	property(fget=is_negative_definite, doc=_doc_positive_definite)

I am not really sure what idea is with this docstring. How would a user access it anyway?