Change loop limit from 20 to dec_maxlen

Author: wannaphong

pythainlp/transliterate/w2p.py

@@ -294,7 +294,7 @@ def _predict(self, word: str) -> str:
         h = last_hidden
 
         preds: list[int] = []
-        for _ in range(20):
+        for _ in range(hp.dec_maxlen):
             h = self._grucell(
                 dec,
                 h,