Bump sphinx-autoapi from 1.8.1 to 1.8.4

Bumps [sphinx-autoapi](https://github.com/readthedocs/sphinx-autoapi) from 1.8.1 to 1.8.4.
- [Release notes](https://github.com/readthedocs/sphinx-autoapi/releases)
- [Changelog](https://github.com/readthedocs/sphinx-autoapi/blob/master/CHANGELOG.rst)
- [Commits](readthedocs/sphinx-autoapi@v1.8.1...v1.8.4)

---
updated-dependencies:
- dependency-name: sphinx-autoapi
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

poetry.lock

@@ -29,7 +29,7 @@ pytest-cov = "^2.11.1"
 jsonschema = "^3.2.0"
 pylint = "^2.10.2"
 sphinx = "^4.1.1"
-sphinx-autoapi = "^1.8.1"
+sphinx-autoapi = "^1.8.4"
 sphinx-rtd-theme = "^0.5.2"
 mypy = "^0.812"