Bump pytest-variables from 1.7.1 to 1.9.0 in /requirements
Bump pytest-variables from 1.7.1 to 1.9.0 in /requirements

Bumps [pytest-variables](https://github.com/pytest-dev/pytest-variables) from 1.7.1 to 1.9.0.
- [Release notes](https://github.com/pytest-dev/pytest-variables/releases)
- [Changelog](https://github.com/pytest-dev/pytest-variables/blob/master/CHANGES.rst)
- [Commits](https://github.com/pytest-dev/pytest-variables/compare/v1.7.1...v1.9.0)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
KWierso/treeherder,KWierso/treeherder,KWierso/treeherder,KWierso/treeherder