Update dependency freezegun to v1.4.0 (#324)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [freezegun](https://togithub.com/spulec/freezegun)
([changelog](https://togithub.com/spulec/freezegun/blob/master/CHANGELOG))
| `==1.3.1` -> `==1.4.0` |
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|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/pypi/freezegun/1.4.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/pypi/freezegun/1.3.1/1.4.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
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|

---

### Release Notes

<details>
<summary>spulec/freezegun (freezegun)</summary>

###
[`v1.4.0`](https://togithub.com/spulec/freezegun/blob/HEAD/CHANGELOG#140)

[Compare
Source](https://togithub.com/spulec/freezegun/compare/1.3.1...1.4.0)

- `asyncio`-support from 1.3.x introduced quite a few bugs, so that
functionality is now hidden behind a flag:
    `with freeze_time('1970-01-02', real_asyncio=True):`

</details>

---

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requirements_dev.txt

@@ -1,7 +1,7 @@
 -e .
 aiohttp==3.9.1
 aiohttp_retry==2.8.3
-freezegun==1.3.1
+freezegun==1.4.0
 mitmproxy==10.1.6
 parameterized==0.9.0
 pdoc==14.2.0