plugin is not automatically removing temporary files

Hello,
The Really Simple CAPTCHA plugin is not automatically removing the images and text files it makes, causing my website to slow down.

I’ve found this topic with the same problem: https://ww.wp.xz.cn/support/topic/plugin-really-simple-captcha-wpfc7_captcha-folder-is-flooded-with-png.

I did what someone in that topic says;
“if so, change lines 70 and 73 to:`
$this->file_mode = 0644;
$this->answer_file_mode = 0640;`
and delete all files manually and check again.”

But that didn’t work. I also tried another piece of code someone suggested in the same topic, also didn’t work. The files are still piling up.

Does anyone have any other suggestions?

https://ww.wp.xz.cn/plugins/really-simple-captcha/