Reduce the batch size in MutualInformationTest to fix the OOMs on Tra…

…vis.

Presumably it also makes it a tiny bit faster. I tested this with 100 different seeds, and it appeared to not be flaky so the smaller batch doesn't appear to exceed the existing test tolerances.

PiperOrigin-RevId: 294506518

tensorflow_probability/python/vi/mutual_information_test.py

@@ -44,7 +44,9 @@ def setUp(self):
         scale=2.0,
         size=[13, 17])
 
-    batch_size, rho, dim = 10000, 0.8, 2
+    batch_size = 1000
+    rho = 0.8
+    dim = 2
     x, eps = tf.split(value=tf.random.normal(shape=(2*batch_size, dim),
                                              seed=self.seed),
                       num_or_size_splits=2, axis=0)