Update ffmpeg comment (#1505)

update ffmpeg comment

nerfstudio/utils/install_checks.py

@@ -28,7 +28,6 @@ def check_ffmpeg_installed():
     if ffmpeg_path is None:
         CONSOLE.print("[bold red]Could not find ffmpeg. Please install ffmpeg.")
         print("See https://ffmpeg.org/download.html for installation instructions.")
-        print("ffmpeg is only necessary if using videos as input.")
         sys.exit(1)