[box-layout] reduce the default animation timeline length
[box-layout] reduce the default animation timeline length

Reduce the default animation timeline length after discussions with design
team.

clutter-project/mx,pwithnall/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,pwithnall/mx,jonnylamb/mx,clutter-project/mx