Add missing tests in the end of: Differentiating conic with PSD and POS constraints

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DiffOpt.jl/test/conic_program.jl

Lines 574 to 578 in edb31fe

	# TODO add a test here, probably on duals
	# # note that there's no change in the PSD slack values or dual optimas
	# @test dy ≈ [0.0, 0.0, 0.0, 0.125978, 0.0, 0.142644, 0.142641, 0.0127401, 0.0, 0.0, 0.0] atol=atol rtol=RTOL
	# @test ds ≈ [0.0, 0.0, -6.66672, 0.0, -3.33336, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0] atol=atol rtol=RTOL
	return

but there are lots of places in the tests that could be improved.

We could potentially roll this into #102. No need to have lots of issues open saying "add a test."