build(deps): bump deepmerge from 3.0.1 to 4.0.0 in /docs

Bumps [deepmerge](https://github.com/toumorokoshi/deepmerge) from 3.0.1 to 4.0.0.
- [Release notes](https://github.com/toumorokoshi/deepmerge/releases)
- [Commits](https://github.com/toumorokoshi/deepmerge/compare/v3.0.1...v4.0.0)

---
updated-dependencies:
- dependency-name: deepmerge
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

docs/requirements.txt

@@ -1,6 +1,6 @@
 click==8.5.0
 colorama==0.4.6
-deepmerge==3.0.1
+deepmerge==4.0.0
 ghp-import==2.1.0
 griffe==2.4.1
 Jinja2==3.1.6