azure-core: remove six dependency

[akx]

Description

This PR removes the dependency on the six Python 2/Python 3 compatibility library in azure-core, as it doesn't use it.

See #36859 for the last attempt about this (autumn 2024), which was approved, and then not merged (?!).
(Also see my previous attempt from 2023, #32248.)

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
  • If other libraries depend on six, they should depend on it explicitly.
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.
  • Since there is no code that uses six in the core library, there is nothing to test.

[github-actions]

Thank you for your contribution @akx! We will review the pull request and get back to you soon.

[azure-sdk]

API change check

API changes are not detected in this pull request.

[Copilot]

PR Overview

This PR removes the dependency on the unused Python 2/3 compatibility library six from azure-core.

• Updated CHANGELOG.md to reflect the removal of six.
• Removed the six dependency from the install_requires section in setup.py.

Reviewed Changes

File	Description
sdk/core/azure-core/CHANGELOG.md	Updated the changelog entry to notify six has been removed.
sdk/core/azure-core/setup.py	Removed six from the install_requires dependency list.

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

[kristapratico]

Hi @akx thanks for making this PR and restarting the discussion about dropping six in azure-core! Our team discussed it, and we are working on making sure a few libraries which still import six (but shouldn't need to) are not impacted by this change. Once we're in the clear, we should be able to merge this. :)

[github-actions]

Hi @akx. Thank you for your interest in helping to improve the Azure SDK experience and for your contribution. We've noticed that there hasn't been recent engagement on this pull request. If this is still an active work stream, please let us know by pushing some changes or leaving a comment. Otherwise, we'll close this out in 7 days.

[akx]

Hello, bot! Yes, this is still a thing!