[pyupgrade] Make example error out-of-the-box (UP046)

[MeGaGiGaGon]

Summary

Part of #18972

This PR makes non-pep695-generic-class (UP046)'s example error out-of-the-box.

Old example

from typing import TypeVar

T = TypeVar("T")


class GenericClass(Generic[T]):
    var: T

New example

from typing import Generic, TypeVar

T = TypeVar("T")


class GenericClass(Generic[T]):
    var: T

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.