Update submodule mavlink to latest Wed May 3 12:39:31 UTC 2023

    - mavlink in PX4/Firmware (9b9117a): mavlink/mavlink@3ee5382
    - mavlink current upstream: mavlink/mavlink@fdef5cc
    - Changes: mavlink/mavlink@3ee5382...fdef5cc

    fdef5cc0 2023-05-03 Nick Exton - common.xml: Prefer COMMAND_INT when command includes altitude field (#1983)
89676d1d 2023-05-03 Nick Exton - common.xml: Add ZOOM_TYPE_HORIZONTAL_FOV to CAMERA_ZOOM_TYPE enum (#1979)