Remove pitch option as it no longer has any effect

* Most likely Microsoft started ignoring it along with the custom SSML
  purge

src/edge_tts/util.py

@@ -83,12 +83,6 @@ async def _async_main() -> None:
         help="lists available voices",
         action="store_true",
     )
-    parser.add_argument(
-        "-p",
-        "--pitch",
-        help="set TTS pitch. Default +0Hz, For more info check https://bit.ly/3eAE5Nx",
-        default="+0Hz",
-    )
     parser.add_argument(
         "-r",
         "--rate",