[3.9] gh-95588: Drop the safety claim from ast.literal_eval docs. (GH-95919)

[miss-islington]

It was never really safe and this claim conflicts directly with the big warning in the docs about it being able to crash the interpreter.
(cherry picked from commit 8baef8a)

Co-authored-by: Gregory P. Smith [email protected]

• Issue: Rephrase ast.literal_eval() to remove any security warranty #95588

Fixes #126711

[Eclips4]

cc @gpshead @ambv

[skirpichev]

See #126711