Update pymdown-extensions requirement from ~=10.3 to ~=10.4

Updates the requirements on [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) to permit the latest version.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](facelessuser/pymdown-extensions@10.3...10.4)

---
updated-dependencies:
- dependency-name: pymdown-extensions
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -10,7 +10,7 @@ mkdocs-material-extensions == 1.3
 mkdocs-minify-plugin ~= 0.7.1
 pip-audit == 2.5.6
 Pygments ~= 2.16.1
-pymdown-extensions ~= 10.3
+pymdown-extensions ~= 10.4
 PyOpenSSL ~= 23.3.0
 wheel ~= 0.41.3
 yamllint == 1.32.0