Merge pyproject.toml changes into RC_v1.6.x

[w-k-jones]

• Have you followed our guidelines in CONTRIBUTING.md?
• Have you self-reviewed your code and corrected any misspellings?
• Have you written documentation that is easy to understand?
• Have you written descriptive commit messages?
• Have you added NumPy docstrings for newly added functions?
• Have you formatted your code using black?
• If you have introduced a new functionality, have you added adequate unit tests?
• Have all tests passed in your local clone?
• If you have introduced a new functionality, have you added an example notebook?
• Have you kept your pull request small and limited so that it is easy to review?
• Have the newest changes from this branch been merged?

[github-actions]

Linting results by Pylint:

Your code has been rated at 8.31/10 (previous run: 8.31/10, +0.00)
_{The linting score is an indicator that reflects how well your code version follows Pylint’s coding standards and quality metrics with respect to the RC_v1.6.x branch.
A decrease usually indicates your new code does not fully meet style guidelines or has potential errors.}