Fix: rename prompt_process.plot output parameter to output_path

[tajpouria]

This update fixes a bug caused by an unrecognized argument in the prompt_process.plot output parameter. To address this issue, the parameter has been renamed to output_path.

[kingljl]

If only renaming output to output_path is not possible, using the cv2. imwrite function at the bottom will result in an error. File name required。

May I ask you a question(请教您个问题)? Do you know how to use fastsam to implement SamAutomaticMaskGenerator to generate multiple masks