Update sphinxcontrib-apidoc requirement

Updates the requirements on [sphinxcontrib-apidoc](https://github.com/sphinx-contrib/apidoc) to permit the latest version.
- [Commits](sphinx-contrib/apidoc@0.3.0...0.4.0)

---
updated-dependencies:
- dependency-name: sphinxcontrib-apidoc
  dependency-type: direct:production
...

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

requirements/docs.txt

@@ -4,7 +4,7 @@ sphinx>=4.2.0, <8.0.0
 sphinx-autodoc-typehints>=1.12.0, <1.21  # limited due to https://github.com/tox-dev/sphinx-autodoc-typehints/issues/260
 sphinx-rtd-theme>=1.0.0, <2.0.0
 myst-parser>=1.0, <3.0
-sphinxcontrib-apidoc>=0.3.0, <0.4.0
+sphinxcontrib-apidoc>=0.3.0, <0.5.0
 nbsphinx>=0.8.5, <0.10.0
 sphinx_design==0.5.0  # Pinning for now as sphinx_design is v.new and still in flux.
 ipykernel>=5.1.0, <7.0.0 # required for executing notebooks via nbsphinx