⬆️ micro: Update serde_repr to v0.1.20 (#1282)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [serde_repr](https://redirect.github.com/dtolnay/serde-repr) |
dev-dependencies | patch | `0.1.19` -> `0.1.20` |
| [serde_repr](https://redirect.github.com/dtolnay/serde-repr) |
dependencies | patch | `0.1.19` -> `0.1.20` |

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### Release Notes

<details>
<summary>dtolnay/serde-repr (serde_repr)</summary>

###
[`v0.1.20`](https://redirect.github.com/dtolnay/serde-repr/releases/tag/0.1.20)

[Compare
Source](https://redirect.github.com/dtolnay/serde-repr/compare/0.1.19...0.1.20)

-   Documentation improvements

</details>

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