Update dependency pdm-backend to v2.4.3 (#316)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [pdm-backend](https://redirect.github.com/pdm-project/pdm-backend) |
build-system.requires | patch | `==2.4.2` -> `==2.4.3` |

---

### Release Notes

<details>
<summary>pdm-project/pdm-backend (pdm-backend)</summary>

###
[`v2.4.3`](https://redirect.github.com/pdm-project/pdm-backend/releases/tag/2.4.3)

[Compare
Source](https://redirect.github.com/pdm-project/pdm-backend/compare/2.4.2...2.4.3)

#####    💻 Chores

- Bump validate-pyproject to 0.9.0  -  by
[@&#8203;henryiii](https://redirect.github.com/henryiii) in
[https://github.com/pdm-project/pdm-backend/issues/265](https://redirect.github.com/pdm-project/pdm-backend/issues/265)
[<samp>(23484)</samp>](https://redirect.github.com/pdm-project/pdm-backend/commit/2348482)
- Update dependencies  -  by
[@&#8203;frostming](https://redirect.github.com/frostming)
[<samp>(7f7dd)</samp>](https://redirect.github.com/pdm-project/pdm-backend/commit/7f7dd51)
- Update badge  -  by
[@&#8203;frostming](https://redirect.github.com/frostming)
[<samp>(6fdd4)</samp>](https://redirect.github.com/pdm-project/pdm-backend/commit/6fdd494)
- Migrate tool config to pyproject.toml  -  by
[@&#8203;frostming](https://redirect.github.com/frostming)
[<samp>(d5d5c)</samp>](https://redirect.github.com/pdm-project/pdm-backend/commit/d5d5c23)

#####     [View changes on
GitHub](https://redirect.github.com/pdm-project/pdm-backend/compare/2.4.2...2.4.3)

</details>

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pyproject.toml

@@ -155,5 +155,5 @@ known-first-party = ["mex", "tests"]
 convention = "google"
 
 [build-system]
-requires = ["pdm-backend==2.4.2"]
+requires = ["pdm-backend==2.4.3"]
 build-backend = "pdm.backend"