[flake8-pyi] Make example error out-of-the-box (PYI062) (#19079)

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## Summary

<!-- What's the purpose of the change? What does it do, and why? -->

Part of #18972

This PR makes [duplicate-literal-member
(PYI062)](https://docs.astral.sh/ruff/rules/duplicate-literal-member/#duplicate-literal-member-pyi062)'s
example error out-of-the-box

[Old example](https://play.ruff.rs/6b00b41c-c1c5-4421-873d-fc2a143e7337)
```py
foo: Literal["a", "b", "a"]
```

[New example](https://play.ruff.rs/1aea839b-9ae8-4848-bb83-2637e1a68ce4)
```py
from typing import Literal

foo: Literal["a", "b", "a"]
```

Imports were also added to the "use instead" section.

## Test Plan

<!-- How was it tested? -->

N/A, no functionality/tests affected

crates/ruff_linter/src/rules/flake8_pyi/rules/duplicate_literal_member.rs

@@ -19,11 +19,15 @@ use crate::{AlwaysFixableViolation, Applicability, Edit, Fix};
 ///
 /// ## Example
 /// ```python
+/// from typing import Literal
+///
 /// foo: Literal["a", "b", "a"]
 /// ```
 ///
 /// Use instead:
 /// ```python
+/// from typing import Literal
+///
 /// foo: Literal["a", "b"]
 /// ```
 ///