Blender Git Loki

Motion Tracking: setting Keyframe A & B was not updating UI indicators

Entering the numbers in the keyframe field was not triggering a viewport
update, so the little green lines down in the cache area were only
change when the user e.g. changed the frame.

Now send appropriate notifiers.

Issue spotted in T86456 by sebastian_k.

Maniphest Tasks: T86456

Differential Revision: https://developer.blender.org/D10963