Update Git Links (#48)

.gitmodules

 [submodule "tutorials/pick_and_place/ROS/src/niryo_one_ros"]
 	path = tutorials/pick_and_place/ROS/src/niryo_one_ros
-	url = git@github.com:NiryoRobotics/niryo_one_ros.git
+	url = https://github.com/NiryoRobotics/niryo_one_ros.git
-	url = git@github.com:ros-planning/moveit_msgs.git
+	url = https://github.com/ros-planning/moveit_msgs.git
-	url = git@github.com:Unity-Technologies/ROS-TCP-Endpoint.git
+	url = https://github.com/Unity-Technologies/ROS-TCP-Endpoint.git

tutorials/pick_and_place/1_urdf.md

 ## Setting up the Unity Scene
 1. Clone this repo to a location on your local machine:
     ```bash
-    git clone --recurse-submodules git@github.com:Unity-Technologies/Unity-Robotics-Hub.git
+    git clone --recurse-submodules https://github.com/Unity-Technologies/Unity-Robotics-Hub.git
     ```
 
 1. Install [Unity Hub](https://unity3d.com/get-unity/download).