DOC: Document FFMpegFileWriter *args, **kwargs

Adds documentation explaining that arguments are forwarded
to the parent MovieWriter class.

Fixes matplotlib#22831

Author: Saumya

lib/matplotlib/animation.py

@@ -605,6 +605,7 @@ def _args(self):
 class FFMpegFileWriter(FFMpegBase, FileMovieWriter):
     """
     File-based ffmpeg writer.
+
     Parameters
     ----------
     *args, **kwargs