MAINT Add to test_identify_names so class property tested

[lucyleeow]

Ensure we get to the else in visit_Attribute:

sphinx-gallery/sphinx_gallery/backreferences.py

Lines 89 to 91 in 451ccba

	else:
	# need to get a in a().b
	self.visit(node)

This is probably tested in test_full.py but nice to have in a more 'unit' test.

[larsoner]

Thanks @lucyleeow !