Update default config in augmentation.config for DS2.

deep_speech_2/augmentation.config

 [
     {
         "type": "noise",
-        "params": {"min_snr_dB": 50,
+        "params": {"min_snr_dB": 40,
                    "max_snr_dB": 50,
                    "noise_manifest": "datasets/manifest.noise"},
         "prob": 0.0
     },
     {
         "type": "speed",
-        "params": {"min_speed_rate": 0.9,
-                   "max_speed_rate": 1.1},
+        "params": {"min_speed_rate": 0.95,
+                   "max_speed_rate": 1.05},
         "prob": 0.0
     },
     {
@@ -24,11 +24,4 @@
                    "max_gain_dBFS": 10},
         "prob": 0.0
     },
-    {
-        "type": "bayesian_normal",
-        "params": {"target_db": -20,
-                   "prior_db": -20,
-                   "prior_samples": 100},
-        "prob": 0.0
-    }
 ]