README: Center family photo (#1122)

Increased size of family photo

README.md

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 # Universal Robots ROS2 Driver
 
 Universal Robots has become a dominant supplier of lightweight, robotic manipulators for industry, as well as for scientific research and education.
-<center><img src="ur_robot_driver/doc/installation/initial_setup_images/family_photo.png" alt="Universal Robot family" style="width: 80%;"/></center>
+<div align="center"><img src="ur_robot_driver/doc/installation/initial_setup_images/family_photo.png" alt="Universal Robot family" style="width: 90%;"/></div>
 
 This is one of the very first ROS2 manipulator drivers. Some of the new features are enabled by ROS2 and include decreased latency, improved security, and more flexibility regarding middleware configuration. The package contains launch files to quickly get started using the driver as a standalone version or in combination with MoveIt2