Increase tolerance for test_EnsemblePosterior (meta-pytorch#2804)

Summary:
This test has been causing test failures in the GitHub CI. I was unable to reproduce this locally on my Mac even with the same pytorch build, so I'm increasing the tolerances a bit here to make this less brittle.

Pull Request resolved: meta-pytorch#2804

Reviewed By: saitcakmak

Differential Revision: D72397870

Pulled By: Balandat

fbshipit-source-id: b612e6b4fd7c522044333b3f10e50e8c99188fe3

Author: Balandat

test/posteriors/test_ensemble.py

@@ -82,8 +82,8 @@ def test_EnsemblePosterior(self):
                 sample_shape=torch.Size((16,)), base_samples=torch.arange(16)
             )
             self.assertEqual(samples.shape, p._extended_shape(torch.Size((16,))))
-            self.assertAllClose(p.mean, samples.mean(dim=0))
-            self.assertAllClose(p.variance, samples.var(dim=0))
+            self.assertAllClose(p.mean, samples.mean(dim=0), rtol=1e-04, atol=1e-06)
+            self.assertAllClose(p.variance, samples.var(dim=0), rtol=1e-04, atol=1e-06)
             # test error on base_samples, sample_shape mismatch
             with self.assertRaises(ValueError):
                 p.rsample_from_base_samples(