Remove unnecessary dependency

Author: chan-1207

turtlebot3_manipulation_bringup/package.xml

@@ -14,7 +14,6 @@
   <author email="[email protected]">Darby Lim</author>
   <author email="[email protected]">Hye-jong KIM</author>
   <buildtool_depend>ament_cmake</buildtool_depend>
-  <exec_depend>gripper_controllers</exec_depend>
   <exec_depend>robot_state_publisher</exec_depend>
   <exec_depend>ros2_control</exec_depend>
   <exec_depend>ros2_controllers</exec_depend>