[pp/ffmpeg] Fix uncaught error if bad --ffmpeg-location is given (#15104)

Revert 9f77e04c76

Closes #12829
Authored by: bashonly

yt_dlp/downloader/external.py

@@ -457,6 +457,8 @@ class FFmpegFD(ExternalFD):
 
     @classmethod
     def available(cls, path=None):
+        # TODO: Fix path for ffmpeg
+        # Fixme: This may be wrong when --ffmpeg-location is used
         return FFmpegPostProcessor().available
 
     def on_process_started(self, proc, stdin):