update en-GB translation
update en-GB translation

Change-Id: I05178c96f43f74d3ccdef212ce7efe99518c661e
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/286123
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms