[Bug] -vsync is still passed down when encoding .webp with ffmpeg

Describe the bug -vsync is no longer reocgnized by ffmpeg 9.0.2, but by selecting any option in the framerate dropdown and saving as WebP in the export menu, ScreentoGif will pass the vsync argument to ffmpeg.

To Reproduce Steps to reproduce the behavior:

1. Export as .webp
2. Use the ffmpeg encoder
3. Select VFR, CFR, or Passththrough in the framerate dropdown
4. See error

Expected behavior A clear and concise description of what you expected to happen.

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: Windows 11 Home edition
• Version: 2.34.2

Additional context Add any other context about the problem here.