Fix Ubuntu instructions
Fix Ubuntu instructions

Hunter522/qgroundcontrol,cfelipesouza/qgroundcontrol,CornerOfSkyline/qgroundcontrol,RedoXyde/PX4_qGCS,dagoodma/qgroundcontrol,CornerOfSkyline/qgroundcontrol,mihadyuk/qgroundcontrol,cfelipesouza/qgroundcontrol,ethz-asl/qgc_asl,mihadyuk/qgroundcontrol,CornerOfSkyline/qgroundcontrol,RedoXyde/PX4_qGCS,remspoor/qgroundcontrol,cfelipesouza/qgroundcontrol,catch-twenty-two/qgroundcontrol,scott-eddy/qgroundcontrol,catch-twenty-two/qgroundcontrol,catch-twenty-two/qgroundcontrol,RedoXyde/PX4_qGCS,remspoor/qgroundcontrol,Hunter522/qgroundcontrol,scott-eddy/qgroundcontrol,dagoodma/qgroundcontrol,Hunter522/qgroundcontrol,dagoodma/qgroundcontrol,scott-eddy/qgroundcontrol,Hunter522/qgroundcontrol,kd0aij/qgroundcontrol,CornerOfSkyline/qgroundcontrol,dagoodma/qgroundcontrol,catch-twenty-two/qgroundcontrol,dagoodma/qgroundcontrol,CornerOfSkyline/qgroundcontrol,mihadyuk/qgroundcontrol,cfelipesouza/qgroundcontrol,mihadyuk/qgroundcontrol,remspoor/qgroundcontrol,scott-eddy/qgroundcontrol,kd0aij/qgroundcontrol,RedoXyde/PX4_qGCS,catch-twenty-two/qgroundcontrol,RedoXyde/PX4_qGCS,dagoodma/qgroundcontrol,remspoor/qgroundcontrol,kd0aij/qgroundcontrol,ethz-asl/qgc_asl,cfelipesouza/qgroundcontrol,cfelipesouza/qgroundcontrol,ethz-asl/qgc_asl,kd0aij/qgroundcontrol,mihadyuk/qgroundcontrol,kd0aij/qgroundcontrol,remspoor/qgroundcontrol,Hunter522/qgroundcontrol,scott-eddy/qgroundcontrol,CornerOfSkyline/qgroundcontrol,catch-twenty-two/qgroundcontrol,RedoXyde/PX4_qGCS,remspoor/qgroundcontrol,ethz-asl/qgc_asl,ethz-asl/qgc_asl,Hunter522/qgroundcontrol,kd0aij/qgroundcontrol,mihadyuk/qgroundcontrol,scott-eddy/qgroundcontrol