Thought that I would jump in to say that another way to change any string in a theme, plugin or even WordPress core is to use the Loco Translate plugin. If you save the generated .po, .mo and .pot files to the /languages folder and not the /loco folder, you can deactivate and delete the plugin when you are finished and your changes will remain intact. I have used this on a couple sites and it is really quite slick and does not require getting one’s “hands dirty” with PHP 🙂
https://wordpress.org/plugins/loco-translate/
Cheers!
Lyle