Changing the Captcha instruction in version 1.7.3

I would like to change the captcha instructions as explained in this thread: https://wordpress.org/support/topic/changing-the-captcha-instruction

This thread indicates that in version 1.7.3 this will be done as an option.

I am running version 1.7.3 and cannot find this option.

On the other hand, I tried to follow the directions to change the code and did not find the line
label for=\”user_captcha\”>Captcha

Instead, I found
label for=\”user_captcha\”>” . $captcha_caption . “

How can I achieve this?

Thanks

Baruch

https://wordpress.org/plugins/blue-captcha/