Update sphinxcontrib-devhelp requirement from <=1.0.2 to <=1.0.6

Updates the requirements on [sphinxcontrib-devhelp](https://github.com/sphinx-doc/sphinxcontrib-devhelp) to permit the latest version.
- [Release notes](https://github.com/sphinx-doc/sphinxcontrib-devhelp/releases)
- [Changelog](https://github.com/sphinx-doc/sphinxcontrib-devhelp/blob/1.0.6/CHANGES)
- [Commits](sphinx-doc/sphinxcontrib-devhelp@1.0.0...1.0.6)

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

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

tests/requirements.txt

@@ -11,7 +11,7 @@ pytest-regressions>=2.0.1
 pytest-timeout>=1.4.2
 sphinx-toolbox[testing]>=2.13.0b3
 sphinxcontrib-applehelp<=1.0.4
-sphinxcontrib-devhelp<=1.0.2
+sphinxcontrib-devhelp<=1.0.6
 sphinxcontrib-htmlhelp<=2.0.1
 sphinxcontrib-jsmath<=1.0.1
 sphinxcontrib-qthelp<=1.0.3