message: Update to use policy.policy_scope to address review comment.
diff: @@ -763,15 +763,12 @@ class AdditiveAttentionTest(test.TestCase, parameterized.TestCase):
  def test_mixed_float16_policy(self):
  # Test case for GitHub issue:
  # https://github.com/tensorflow/tensorflow/issues/46064
  - try:
  - policy.set_policy('mixed_float16')
  + with policy.policy_scope('mixed_float16'):
  q = math_ops.cast(random_ops.random_uniform((2, 3, 4), seed=1), 'float16')
  v = math_ops.cast(random_ops.random_uniform((2, 3, 4), seed=2), 'float16')
  k = math_ops.cast(random_ops.random_uniform((2, 3, 4), seed=3), 'float16')
  layer = dense_attention.AdditiveAttention(causal=True)
  _ = layer([q, v, k])
  - finally:
  - policy.set_policy('float32')
  @combinations.generate(combinations.combine(mode=['graph', 'eager']))
  