test(aliby): fix numpy array comparison in test_image

WHY IS THIS CHANGE NEEDED?:
- https://git.ecdf.ed.ac.uk/swain-lab/aliby/aliby/-/jobs/56767 failed
  because ValueError: The truth value of a Array is ambiguous.

HOW DOES THE CHANGE SOLVE THE PROBLEM?:
- use numpy.array_equal() to compare arrays instead

REFERENCES:
- issue #53

tests/aliby/pipeline/test_image.py

@@ -34,6 +34,6 @@ def test_pad_array(sample_da, dim, n_empty_slices):
     ]
 
     # Checks that original image array is there and is at the last index
-    assert padded_da.compute()[ix] == sample_da
+    assert np.array_equal(padded_da.compute()[ix], sample_da)
     # Checks that the additional axis is extended correctly
     assert padded_da.compute.shape[dim] == n_empty_slices + 1