[flake8-use-pathlib] Make example error out-of-the-box (PTH210) (#19189)

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## Summary

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

Part of #18972

This PR makes [invalid-pathlib-with-suffix
(PTH210)](https://docs.astral.sh/ruff/rules/invalid-pathlib-with-suffix/#invalid-pathlib-with-suffix-pth210)'s
example error out-of-the-box.

[Old example](https://play.ruff.rs/d45720cc-fd08-4443-820f-b3bc9756ac59)
```py
path.with_suffix("py")
```

[New example](https://play.ruff.rs/4103669e-19c5-464a-a3fb-6e7d190ce5fd)
```py
from pathlib import Path

path = Path()

path.with_suffix("py")
```

The "Use instead" section was also modified similarly.

## Test Plan

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

N/A, no functionality/tests affected

crates/ruff_linter/src/rules/flake8_use_pathlib/rules/invalid_pathlib_with_suffix.rs

@@ -19,12 +19,20 @@ use ruff_text_size::Ranged;
 /// ## Example
 ///
 /// ```python
+/// from pathlib import Path
+///
+/// path = Path()
+///
 /// path.with_suffix("py")
 /// ```
 ///
 /// Use instead:
 ///
 /// ```python
+/// from pathlib import Path
+///
+/// path = Path()
+///
 /// path.with_suffix(".py")
 /// ```
 ///