Fix link to codecov

README.md

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 # kinematics_interface
 [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
-[![codecov](https://codecov.io/gh/ros-controls/kinematics_interface/branch/humble/graph/badge.svg?token=NS73VKPG9V)](https://codecov.io/gh/ros-controls/kinematics_interface)
+[![codecov](https://codecov.io/gh/ros-controls/kinematics_interface/branch/humble/graph/badge.svg?token=NS73VKPG9V)](https://codecov.io/gh/ros-controls/kinematics_interface/tree/humble)
 
 This is a ROS 2 package for using C++ kinematics frameworks in the context of ROS 2 control. A kinematics interface is designed to allow ROS 2 controllers to control robots in Cartesian space. This package also contains a basic implementation of the interface using KDL.