Fix ResourceWarning: unclosed file <_io.BufferedWriter name=5>

https://forums.ankiweb.net/t/aqt-sound-py-resourcewarning-unclosed-file-io-bufferedwriter-name-5/13070

qt/aqt/sound.py

@@ -321,6 +321,8 @@ class SimpleProcessPlayer(Player):  # pylint: disable=abstract-method
                 self._process.wait(0.1)
                 if self._process.returncode != 0:
                     print(f"player got return code: {self._process.returncode}")
+                if self._process.stdin:
+                    self._process.stdin.close()
                 self._process = None
                 return
             except subprocess.TimeoutExpired: