Reduce accuracy of surface-order test

Test is flaky.
Test makes sure ERT does not change order of arrays and numerical
accuracy is not important.

tests/integration_tests/analysis/test_es_update.py

@@ -186,7 +186,7 @@ def sample_prior(nx, ny):
         with pytest.raises(AssertionError):
             np.testing.assert_array_equal(surf_prior[i], surf_posterior[i])
         np.testing.assert_almost_equal(
-            surf_prior[i].values, surf_posterior[i].values, decimal=3
+            surf_prior[i].values, surf_posterior[i].values, decimal=2
         )