Your code is showing an empty space in the hook name
add_action('wp_set_comment_status ', 'update_business_rating_avg');
^
try removing it
add_action('wp_set_comment_status', 'update_business_rating_avg');
Your code is showing an empty space in the hook name
add_action('wp_set_comment_status ', 'update_business_rating_avg');
^
try removing it
add_action('wp_set_comment_status', 'update_business_rating_avg');