fix: remove duplicate .replace mid-tone in _clean_ipa (#1409)

The second .replace mid-tone removal on line 31 is identical to
line 30 and is dead code. After line 30 removes all mid-tone
characters, line 31 has no effect.

Author: zichen0116

pythainlp/soundex/sound.py

@@ -28,7 +28,6 @@ def _clean_ipa(ipa: str) -> str:
         .replace("˨˩", "")
         .replace("˦˥", "")
         .replace("˧", "")
-        .replace("˧", "")
         .replace(" .", ".")
         .replace(". ", ".")
         .strip()