fix wavegrad test

tests/test_wavegrad_train.py

@@ -1,5 +1,6 @@
 import unittest
 
+import numpy as np
 import torch
 from torch import optim
 from TTS.vocoder.models.wavegrad import Wavegrad
@@ -33,7 +34,8 @@ class WavegradTrainTest(unittest.TestCase):
                                          [1, 2, 4, 8]])
         model.train()
         model.to(device)
-        model.compute_noise_level(1000, 1e-6, 1e-2)
+        betas = np.linspace(1e-6, 1e-2, 1000)
+        model.compute_noise_level(betas)
         model_ref.load_state_dict(model.state_dict())
         model_ref.to(device)
         count = 0