A typo correction (backport ros2#2277) (ros2#2278)

Co-authored-by: YogeshMaan <[email protected]>

Author: mergify[bot]

source/Roadmap.rst

@@ -74,7 +74,7 @@ If you'd like to take on one of these tasks, please :doc:`get in touch with us <
    * - Developer experience: Better integration of ROS 2 repos with package managers and documentation for building/running ROS 2 applications.
      - Large
      - iRobot
-     - 2th quarter 2022
+     - 2nd quarter 2022
    * - Develop a system level QoS/network debugging tool
      - Large
      - Open Robotics