If you want to keep your Hostinger user account and only deactivate your hosting, you can do so easily by going to the Hosting → Manage → Deactivate Account:
Keep in mind that deactivating an account means that all files, databases, emails, and any configuration will be lost. In case you need backups before canceling hosting - be sure to download them beforehand.
You will be asked a few questions, and have an option to cancel your hosting account at the expiration date:
How to reactivate your hosting account?
If your hosting account isn't due expiration yet, you will now see it on the Hosting page with Pending delete status:
If you would like to proceed with deactivation, click on Delete
If you changed your mind, click on Restore
NOTE:
To remove all data from the Hostinger profile, check this article: Can I delete my whole Hostinger profile?