Update Gaia API documents for #e8e13bc9ff1077acb8d0fc33bdbc2c428560f366
    Bug 950070 - Perform correct localization of the roaming notifier on lockscreen

The localize() method takes as a third argument an object, not a string.
Doing this like this results in a lockscreen not substituting correctly
and hence displaying ``{{operator}} (Roaming)'' to the user.