'ControllerMock::update' hides overloaded virtual function

[christophfroehlich]

On humble I saw the following warning (but code is the same on master branch)

In file included from /workspaces/ros2_humble_ws/src/ros2_control/controller_manager/test/test_hardware_spawner.cpp:23:
/workspaces/ros2_humble_ws/src/ros2_control/controller_manager/test/controller_manager_test_common.hpp:259:16: warning: 'ControllerMock::update' hides overloaded virtual function [-Woverloaded-virtual]
  MOCK_METHOD0(update, controller_interface::return_type(void));