Unchecking the default site settings: Auto-assign items

Hi there,
I’m trying to edit the file SiteSettingsForm.php under src > Form so that the Auto-Assign items isn’t checked by default. I tried the obvious first, changing “true” to “false”, but that didn’t work upon updating and clearing my site’s cache. Then I tried to model off of others in that file ‘value’ => $settings->get(‘o:assign_new_items’), but that didn’t work either. I also tried duplicating this file and putting it under my specific theme’s folder, but that failed as well.

Does anyone have any other suggestions? I was able to uncheck the other settings very easily, but for some reason, this Auto-assign items is tough.