Clean up MozL10n API use in Cost Control #1057795

This is relating bug 1057795
navigator.mozL10n.setAttributes does not return any value. Please, read https://developer.mozilla.org/en-US/docs/Web/API/L10n.setAttributes documentation.

The first attribute is supposed to be a DOM Node. You're passing an empty variable

Please, revert those changes.

You can only really fix scenarios where _() is used to assign value to node.textContent.