Remove `timingFunction` definition and add `calculationMode`
Remove `timingFunction` definition and add `calculationMode`

The property `timingFunction` is ignored in keyframe animations since
the property `keyframes` must be defined. The property
`calculationMode`, seemingly, defaults to `kCAAnimationLinear` but I
want to make it clear that this property affects the behavior of the
animation.

jkereako/LoginView