Fix test_mult_norm_call_types on 32-bit systems (matplotlib#30629)

In that case, the default int is also 32-bit, so the test will fail to
be equal to `int64`. So instead of the implicit type, use an explicit
one.

Author: QuLogic

lib/matplotlib/tests/test_colors.py

@@ -2016,7 +2016,7 @@ def test_mult_norm_call_types():
                               [[0., 0.5, 1.],
                                [1, 3, 5]])
     assert no_norm_out[0].dtype == np.dtype('float64')
-    assert no_norm_out[1].dtype == np.dtype('int64')
+    assert no_norm_out[1].dtype == vals.dtype
 
     # test with NoNorm, structured array as input
     mn_no_norm = mpl.colors.MultiNorm(['linear', mcolors.NoNorm()])