Currently, the only way of uninstalling the extension is via the command line. You can uninstall the module by running following commands inside Magento's installation base directory.

Note: Before running the bin/magento command make sure the file is executable.

bin/magento module:uninstall Nosto_Tagging
bin/magento setup:upgrade
bin/magento cache:clean
bin/magento setup:di:compile

After the extension is uninstalled you still need to remove the package from your Magento dependencies using Composer. If you don't have composer installed yet you can get it by following these instructions. It's recommended to install composer globally. Once you have composer installed you can uninstall the Nosto extension (nosto/module-nostotagging).

composer remove nosto/module-nostotagging