Pontoon: Update English (Great Britain) (en-GB) localization of AMO Frontend
Pontoon: Update English (Great Britain) (en-GB) localization of AMO Frontend

Localization authors:
- Ian Neal <iann_bugzilla@blueyonder.co.uk>

tsl143/addons-frontend,kumar303/addons-frontend,mozilla/addons-frontend,tsl143/addons-frontend,kumar303/addons-frontend,mozilla/addons-frontend,mozilla/addons-frontend,kumar303/addons-frontend,tsl143/addons-frontend,tsl143/addons-frontend,kumar303/addons-frontend,mozilla/addons-frontend