Add pytest-randomly

[mhucka]

pytest-randomly is a Pytest plugin that helps find hidden order dependencies in test suites by randomly shuffling tests and resetting Python's random seed. It prevents bugs where one test unintentionally relies on the state left behind by a previous test.

This is generally a good practice. No Qualtran test failures currently happen from adding to the set of pytest plugins used.

[gemini-code-assist]

Code Review

This pull request updates the pyproject.toml file to add pytest-randomly to the test dependencies and removes a trailing newline at the end of the file. There are no review comments, and I have no feedback to provide.