revert commit, use SyncBatchNormalization cause nan in FastSpeechPostnet

Author: dathudeptrai

tensorflow_tts/models/fastspeech.py

@@ -517,7 +517,8 @@ def __init__(self, config, **kwargs):
                 padding="same",
                 name="conv_._{}".format(i),
             )
-            batch_norm = tf.keras.layers.experimental.SyncBatchNormalization(
+            batch_norm = tf.keras.layers.BatchNormalization(
+                axis=-1,
                 name="batch_norm_._{}".format(i)
             )
             self.conv_batch_norm.append((conv, batch_norm))