[README] Replace "git submodule" with "git clone".
[README] Replace "git submodule" with "git clone".

geoffreychiou/industrial_ci,ros-industrial/industrial_ci,ros-industrial/industrial_ci,ubi-agni/industrial_ci,geoffreychiou/industrial_ci,tecnalia-advancedmanufacturing-robotics/industrial_ci,ros-industrial/industrial_ci,tecnalia-advancedmanufacturing-robotics/industrial_ci,ubi-agni/industrial_ci,tecnalia-advancedmanufacturing-robotics/industrial_ci