Add a note about PEP 621 not yet being support for Poetry projects

[edgarrmondragon]

Why:

Partial support for Poetry 2 was added in dependabot/dependabot-core#11642, but the project section is not yet supported.

Closes:

What's being changed (if available, include any code snippets, screenshots, or gifs):

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• The changes in this PR meet the docs fundamentals that are required for all content.
• All CI checks are passing and the changes look good in the review environment.

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Pull Request Overview

This PR adds a note to clarify that the project section defined by PEP 621 is not yet supported for Poetry projects.

• Added an important note regarding PEP 621 support for Poetry in the supported package managers documentation
• Updated the reusables file to reflect the current state of dependency support

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Source	Review	Production	What Changed
code-security/dependabot/ecosystems-supported-by-dependabot/supported-ecosystems-and-repositories.md	fpt ghec ghes@ 3.16 3.15 3.14 3.13 3.12	fpt ghec ghes@ 3.16 3.15 3.14 3.13 3.12	from reusable

Key: fpt: Free, Pro, Team; ghec: GitHub Enterprise Cloud; ghes: GitHub Enterprise Server

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[Sharra-writes]

Thanks so much for opening a PR! I'll get this triaged for review