In order to remove the GTranslate application from your Shopify e-shop.
Make sure that on GTranslate app settings page "Show floating language selector" option is set to No.
Delete GTranslate app from the list of your applications.
If you have already uninstalled GTranslate without disabling the "Show floating language selector" option, you should install GTranslate back, and follow the already described process of removing the application.
If for some reason you do not want to install GTranslate again, then you should open your theme.liquid file from Online Store → Current Theme → Actions → Edit Code, and find and delete {% include 'gtranslate' %} snippet from the end of that file.