Hi,
It definitely works. This modification has been used by many users before you.
You must have another problem. For example, maybe you did it for another language than the one on your frontend. Or maybe you have an error in the language override file. If there is an error somewhere in a language file, the language file will be ignored by Joomla.
You can activate the "debug languages" setting of the Joomla configuration and then look at the page on the frontend. At the bottom, you'll see the debug area and it will tell you if there is an error in the override file.