build(deps): bump pytest-html in /testing/plugins_integration

Bumps [pytest-html](https://github.com/pytest-dev/pytest-html) from 3.0.0 to 3.1.0.
- [Release notes](https://github.com/pytest-dev/pytest-html/releases)
- [Changelog](https://github.com/pytest-dev/pytest-html/blob/master/CHANGES.rst)
- [Commits](https://github.com/pytest-dev/pytest-html/compare/v3.0.0...v3.1.0)

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

testing/plugins_integration/requirements.txt

@@ -5,7 +5,7 @@ pytest-bdd==4.0.1
 pytest-cov==2.10.1
 pytest-django==4.1.0
 pytest-flakes==4.0.3
-pytest-html==3.0.0
+pytest-html==3.1.0
 pytest-mock==3.3.1
 pytest-rerunfailures==9.1.1
 pytest-sugar==0.9.4