[pylint] Make example error out-of-the-box (PLE1507)

[MeGaGiGaGon]

Summary

Part of #18972

This PR makes invalid-envvar-value (PLE1507)'s example error out-of-the-box.

Old example

os.getenv(1)

New example

import os

os.getenv(1)

The "Use instead" section was also updated similarly.

Test Plan

N/A, no functionality/tests affected

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.