Update dependency pytest-asyncio to v0.21.1 (#212)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [pytest-asyncio](https://togithub.com/pytest-dev/pytest-asyncio)
([changelog](https://pytest-asyncio.readthedocs.io/en/latest/reference/changelog.html))
| `==0.21.0` -> `==0.21.1` |
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|
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|
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|
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|

---

### Release Notes

<details>
<summary>pytest-dev/pytest-asyncio (pytest-asyncio)</summary>

###
[`v0.21.1`](https://togithub.com/pytest-dev/pytest-asyncio/releases/tag/v0.21.1):
pytest-asyncio 0.21.1

[Compare
Source](https://togithub.com/pytest-dev/pytest-asyncio/compare/v0.21.0...v0.21.1)

### 0.21.1 (2023-07-12)

- Output a proper error message when an invalid `asyncio_mode` is
selected.
- Extend warning message about unclosed event loops with additional
possible cause.

[#&#8203;531](https://togithub.com/pytest-dev/pytest-asyncio/issues/531)
- Previously, some tests reported "skipped" or "xfailed" as a result.
Now all tests report a "success" result.

</details>

---

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requirements_dev.txt

@@ -8,7 +8,7 @@ pdoc==14.0.0
 pydantic==1.10.11
 pytest==7.4.0
 pytest-aiohttp==1.0.4
-pytest-asyncio==0.21.0
+pytest-asyncio==0.21.1
 pytest-cov==4.1.0
 pytest-golden==0.2.2
 pytest-mock==3.11.1