[deps]: Update Rust crate async-trait to v0.1.81 (#880)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [async-trait](https://togithub.com/dtolnay/async-trait) | dependencies
| patch | `0.1.80` -> `0.1.81` |

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### Release Notes

<details>
<summary>dtolnay/async-trait (async-trait)</summary>

###
[`v0.1.81`](https://togithub.com/dtolnay/async-trait/releases/tag/0.1.81)

[Compare
Source](https://togithub.com/dtolnay/async-trait/compare/0.1.80...0.1.81)

- Turn off unneeded features of `syn` dependency
([#&#8203;272](https://togithub.com/dtolnay/async-trait/issues/272),
thanks [@&#8203;klensy](https://togithub.com/klensy))

</details>

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