[3.14] gh-62480: De-personalize "Mocking Unbound Methods" section in `unittest.mock` examples (GH-141322) (#141324)

gh-62480: De-personalize "Mocking Unbound Methods" section in `unittest.mock` examples (GH-141322)

* Rewrite Mocking Unbound Methods paragraph to second person
(cherry picked from commit ec85d3cbfe315086805c33bb64c28a8509098829)

Co-authored-by: Elena O <31424287+oklena@users.noreply.github.com>
Co-authored-by: C.A.M. Gerlach <CAM.Gerlach@Gerlach.CAM>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>