Move from dev-dependencies to poetry group specification

[d33bs]

Description

This PR moves the pyproject.toml file to use Poetry's "group dependency" specification (see "A note about defining a dev dependencies group"). The existing dev-dependencies table in the pyproject.toml file is synonymous with the dev group, and this change updates the table name to reflect updated Poetry nomenclature + documentation.

What is the nature of your change?

• Bug fix (fixes an issue).
• Enhancement (adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• This change requires a documentation update.

Checklist

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• I have read the CONTRIBUTING.md guidelines.
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• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• New and existing unit tests pass locally with my changes.
• I have added tests that prove my fix is effective or that my feature works.
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[gwaybio]

LGTM, but @kenibrewer might have better feedback.

[d33bs]

Thank you @gwaybio for the review! Merging this in. @kenibrewer please don't hesitate to let me know if we may have missed something here.

[kenibrewer]

LGTM