[3.14] gh-107194: Improved language of list.index in tutorial (gh-138518) (#138527)

gh-107194: Improved language of list.index in tutorial (gh-138518)
(cherry picked from commit f19f1d8563fb3abbb673812f16e2be5f10af42e4)

Co-authored-by: Ric <11750904+ricsatjr@users.noreply.github.com>