Update submodule gz to latest Sun Apr 14 06:50:08 UTC 2024

    - gz in PX4/Firmware (4abb4e7): PX4/PX4-gazebo-models@6b4ed09
    - gz current upstream: PX4/PX4-gazebo-models@d754381
    - Changes: PX4/PX4-gazebo-models@6b4ed09...d754381

    d754381 2024-04-10 Frederik Markus - Fix altitude to elevation (#32)
3018aa8 2024-04-10 Sergei Grichine - Adding lawn.sdf world to have sky and grassy ground plane for rovers (#35)
c3905a7 2024-03-27 Celil Buğra Karacan - Add headless mode to simulation-gazebo (#37)
14d9c68 2024-03-14 Beniamino Pozzan - fix(worlds): replace deprecated GzScene3D plugin (#25)