Fix test_incompatible_dimensions test (SciTools#3977)

* test_incompatible_dimensions used a ragged array for the test, which has been deprecated in numpy, and now fails if dtype is anything other than object.  This test appears to be checking that the addition of a [2x4] masked array to a [2x3] masked cube should raise a ValueError. This commit fixes the creation of `data3` object to be a [2x4] non-ragged array.

* Added entry to what's new

* Added name to core developer list :)

* Update latest.rst

Fixed space in PR macro call

lib/iris/tests/test_basic_maths.py

@@ -853,7 +853,7 @@ def setUp(self):
 
     def test_incompatible_dimensions(self):
         data3 = ma.MaskedArray(
-            [[3, 3, 3, 4], [2, 2, 2]], mask=[[0, 1, 0, 0], [0, 1, 1]]
+            [[3, 3, 3, 4], [2, 2, 2, 2]], mask=[[0, 1, 0, 0], [0, 1, 1, 1]]
         )
         with self.assertRaises(ValueError):
             # Incompatible dimensions.