Level sequence updates more than once per frame when content editors are open

When content editors are open, they cause sequencer to be updated more than once per frame. This causes animations running in PIE to play faster than expected. Licensee provides code for a potential fix, as well as repro steps.

1. Open TM-Sequence_CurveEditor map
2. Edit the level blueprint.
3. In the "Create Level Sequence Player" node select the "Sequencer_CurveEditor" as the sequencer to create.
4. Call the "Play Looping" function on the created level sequence player.
5. Play the level and notice the play rate of the ball bouncing. Note that this is the normal play rate.
6. Now open as many UMG Widget Blueprints (i.e. UMG_ScrollBox, UMG_Checkbox_Appearance, etc. etc.)
7. Play the level again, notice that the play rate is much faster.