robots.txt return No user-agent specified

Hello,
I have seen that google has an problem with the robots.txt rules.

“Disallow: /wp-content/uploads/wpo-plugins-tables-list.json

Gives me: No user-agent specified

I read in another thread that this pluging is generating this, and that we should add:
add_filter( ‘wpo_update_plugin_json’, ‘__return_false’ );

But I don′t know where?
I put it like this and that second line is not working. I do not know how to code.

Disallow: /wp-content/uploads/wpo-plugins-tables-list.json
add_filter( ‘wpo_update_plugin_json’, ‘__return_false’ );

Is it true that despite some of this information already being publicly available, providing a file like this is just inviting brute force campaigns? I am having plenty of haking attemps daily.

The page I need help with: [log in to see the link]