Update dependency pymdown-extensions to v10.4 (#635)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
|
[pymdown-extensions](https://togithub.com/facelessuser/pymdown-extensions)
| minor | `==10.3.1` -> `==10.4` |

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### Release Notes

<details>
<summary>facelessuser/pymdown-extensions (pymdown-extensions)</summary>

###
[`v10.4`](https://togithub.com/facelessuser/pymdown-extensions/releases/tag/10.4)

[Compare
Source](https://togithub.com/facelessuser/pymdown-extensions/compare/10.3.1...10.4)

#### 10.4

- **NEW**: Snippets: Allow PathLike objects for `base_path` to better
support interactions with MkDocs.
-   **FIX**: Block Admonitions: Empty titles should be respected.
-   **FIX**: Block Details: Empty summary should be respected.

</details>

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.github/workflows/mkdocs-requirements.txt

@@ -10,7 +10,7 @@ mkdocs-macros-plugin==1.0.5
 mkdocs-material==9.4.8
 mkdocs-material-extensions==1.3
 Pygments==2.16.1
-pymdown-extensions==10.3.1
+pymdown-extensions==10.4
 python-dateutil==2.8.2
 PyYAML==6.0.1
 repackage==0.7.3