Update submodule mavlink to latest Tue Apr 2 12:40:33 UTC 2024

    - mavlink in PX4/Firmware (9bf8b1a): mavlink/mavlink@a3558d6
    - mavlink current upstream: mavlink/mavlink@4e5d6a2
    - Changes: mavlink/mavlink@a3558d6...4e5d6a2

    4e5d6a25 2024-03-27 Hamish Willee - DO_FENCE_ENABLE when sent as a command (#2091)
fabfb1dc 2024-03-21 Peter Barker - common.xml: deprecate the _INT frames (#2092)
a13a8de9 2024-03-21 Julian Oes - common: trying to make sense of radius unit (#2097)
1f084f1b 2024-03-20 Marek S. Łukasiewicz - SIM_STATE specify attitude units as rad (#2095)