BUG: Duplicate merge of _controllers in Flight.TimeNodes.merge()

[zuorenchen]

Describe the bug

Duplicate merge of _controllers in Flight.TimeNodes.merge()

To Reproduce

https://github.com/RocketPy-Team/RocketPy/blame/9cf3dd4817f00609f227009c7249cfe260cf74b3/rocketpy/simulation/flight.py#L3746

Expected behavior

Line 3746 should be removed

Screenshots

Additional context

Add any other context about the problem here.

[Gui-FernandesBR]

great suggestion, can you propose a PR?