update en-GB translation
update en-GB translation

Change-Id: I3b115ac47fb92d5c0424ffb0890dc88590926889
Reviewed-on: https://gerrit.instructure.com/206339
Tested-by: Jenkins

djbender/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms