When the Subscribers Shopify app is removed from your store, technically, all Subscribers scripts get automatically removed from your theme.
However, there is a place in your site where Subscribers Liquid code (automatically added by the Assets API when the Subscribers app is installed on your store) gets left behind.
Please note that these remnant codes do not affect your storefront and site performance in any way. However, if you wish to totally remove all Subscribers-related codes from your store, please follow these instructions:
1. From your Shopify store's admin dashboard, go to "Themes" and then use the "Actions" drop-down menu to navigate to "Edit code" as shown below:
2. Locate and then click on either the layout.liquid or theme.liquid file as shown below:
3. Locate and remove all Subscribers-related scripts from the file:
Once the Subscribers scripts have been deleted, make sure to click the "Save" button before exiting the file editor.