It is very rare but there might be some leftover code of the Product Labels Pro app when you already uninstalled the app.
No worries, please follow some simple steps to remove it all.
To uninstall the app, please go to Admin ⇒ Apps => Product Labels Pro.
In case you forget to Restore all content from theme, you can delete the code by editing the theme.
Go to file: layout/theme.liquid
Find the code {% include 'bss-product-labels-configs' %} and remove it.
Also, remove:
templates/search.bss.product.labels.liquid
snippets/bss-product-labels-configs.liquid
assets/bss_product_labels.js.liquid
Then, Delete the app.
Let us know at sales@bsscommerce.com if you cannot find the code. We are willing to help you.