⬆️ micro: Update syn to v2.0.91 (#1182)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [syn](https://redirect.github.com/dtolnay/syn) | dependencies | patch
| `2.0.90` -> `2.0.91` |

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### Release Notes

<details>
<summary>dtolnay/syn (syn)</summary>

###
[`v2.0.91`](https://redirect.github.com/dtolnay/syn/releases/tag/2.0.91)

[Compare
Source](https://redirect.github.com/dtolnay/syn/compare/2.0.90...2.0.91)

- Support parsing `Vec<Arm>` using `parse_quote!`
([#&#8203;1796](https://redirect.github.com/dtolnay/syn/issues/1796),
[#&#8203;1797](https://redirect.github.com/dtolnay/syn/issues/1797))

</details>

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