fix ffplay arguments

Author: d-loose

src/piper/audio_playback.py

@@ -22,10 +22,10 @@ def __enter__(self):
                 "-autoexit",
                 "-f",
                 "s16le",
-                "-ar",
+                "-sample_rate",
                 str(self.sample_rate),
-                "-ac",
-                "1",
+                "-ch_layout",
+                "mono",
                 "-",
             ],
             stdin=subprocess.PIPE,