sitl_gazebo: update submodule
sitl_gazebo: update submodule

This should fix a race because the use of future/promise wasn't done in
a thread-safe way.

mje-nz/PX4-Firmware,acfloria/Firmware,PX4/Firmware,PX4/Firmware,dagar/Firmware,acfloria/Firmware,acfloria/Firmware,acfloria/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,dagar/Firmware,PX4/Firmware,acfloria/Firmware,dagar/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,mje-nz/PX4-Firmware,PX4/Firmware,PX4/Firmware,acfloria/Firmware,krbeverx/Firmware,dagar/Firmware,dagar/Firmware,krbeverx/Firmware,acfloria/Firmware,PX4/Firmware