Remove test for unsupported feature

pystencils_tests/test_interpolation.py

@@ -242,5 +242,3 @@ def test_spatial_derivative():
 
     diff = sympy.diff(x.interpolated_access((tx.center, ty.center)), tx.center)
     print("diff: " + str(diff))
-    diff = sympy.diff(x.interpolated_access((tx.center, 2 * ty.center)), sympy.Matrix((tx.center, ty.center)))
-    print("diff: " + str(diff))