Adjust default to be able to process longer sentences (coqui-ai#1835)

Running `tts --text "$text" --out_path …` with a somewhat longer
sentences in the text will lead to warnings like “Decoder stopped with
max_decoder_steps 500” and the sentences just being cut off in the
resulting WAV file.

This happens quite frequently when feeding longer texts (e.g. a blog
post) to `tts`. It's particular frustrating since the error is not
always obvious in the output. You have to notice that there are missing
parts. This is something other users seem to have run into as well [1].

This patch simply increases the maximum number of steps allowed for the
tacotron decoder to fix this issue, resulting in a smoother default
behavior.

[1] mozilla/TTS#734

TTS/tts/configs/tacotron_config.py

@@ -162,7 +162,7 @@ class TacotronConfig(BaseTTSConfig):
     stopnet: bool = True
     separate_stopnet: bool = True
     stopnet_pos_weight: float = 0.2
-    max_decoder_steps: int = 500
+    max_decoder_steps: int = 10000
     encoder_in_features: int = 256
     decoder_in_features: int = 256
     decoder_output_dim: int = 80