Update layer norm eps

This PR updates the layernorm epsilon value to reflect the original implementation.

This was tested with

@ydshieh

and integration tests are not affected (logits still match).

config.json

@@ -209,7 +209,7 @@
       "LABEL_0": 0,
       "LABEL_1": 1
     },
-    "layer_norm_eps": 1e-05,
+    "layer_norm_eps": 1e-6,
     "length_penalty": 1.0,
     "max_length": 20,
     "min_length": 0,