Loosen too-tight lpdft grad rohf san test tol

I think it was a typo because all the other rohf grad san tests
had 6 already

Author: MatthewRHermes

pyscf/grad/test/test_grad_lpdft.py

@@ -284,7 +284,7 @@ def test_rohf_sanity (self):
                 de = mc_grad.kernel(state=i)[1, 0]
                 self.assertAlmostEqual(de, NUM_REF[i], 4)
                 de_ref = mc_grad_ref.kernel(state=i)[1, 0]
-                self.assertAlmostEqual (de, de_ref, 8)
+                self.assertAlmostEqual (de, de_ref, 6)
 
     def test_dfrohf_sanity (self):
         n_states = 3