Update submodule sitl_gazebo to latest Sat May  1 00:38:24 UTC 2021
Update submodule sitl_gazebo to latest Sat May  1 00:38:24 UTC 2021

    - sitl_gazebo in PX4/Firmware (283138e87d46e573ce101033e01a59b273430928): https://github.com/PX4/PX4-SITL_gazebo/commit/05e2cd9c03ffa77f0c0d5bd3e788d33e06480b25
    - sitl_gazebo current upstream: https://github.com/PX4/PX4-SITL_gazebo/commit/4c27fc7dd659c262257abeea2308e2f1c54e9029
    - Changes: https://github.com/PX4/PX4-SITL_gazebo/compare/05e2cd9c03ffa77f0c0d5bd3e788d33e06480b25...4c27fc7dd659c262257abeea2308e2f1c54e9029

    4c27fc7 2021-04-20 JaeyoungLim - Update mavsdk versions for firmware SITL tests (#741)

acfloria/Firmware,acfloria/Firmware,acfloria/Firmware,acfloria/Firmware,acfloria/Firmware,acfloria/Firmware,acfloria/Firmware