Fix doc typo

doc/source/index.rst

orientation/Orientation_two_markers.rst

orientation/bumblebee_orientation.rst

orientation/examples/bumblebee_markers.py

orientation/examples/bumblebee_thorax_orientation.py

orientation/examples/triangle_isocel.py

orientation/examples/triangle_pitch.py

orientation/examples/two_markers.py

orientation/examples/yawpitchroll.py

orientation/index.rst

orientation/media/marked_bumblebee.png

orientation/orientation.rst

orientation/rotation.rst