remove testing entry from groot PR

Author: gramss

tutorials/index.rst

@@ -11,7 +11,6 @@ Navigation2 Tutorials
    docs/camera_calibration.rst
    docs/get_backtrace.rst
    docs/groot.rst
-   docs/intro_testing.rst
    docs/navigation2_on_real_turtlebot3.rst
    docs/navigation2_with_slam.rst
    docs/navigation2_with_stvl.rst