Swap pip-args with extra-pip-args

[agalazis]

pip-args should be extra-pip-args

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The issue

I followed the instructions to speedup my build. pip-args is not accepted with a cryptic error {}

The fix

I have found through another doc page that extra-pip-args is the flag:
https://pipenv.pypa.io/en/latest/advanced.html

The checklist

• Associated issue
• A news fragment in the news/ directory to describe this fix with the extension .bugfix.rst, .feature.rst, .behavior.rst, .doc.rst. .vendor.rst. or .trivial.rst (this will appear in the release changelog). Use semantic line breaks and name the file after the issue number or the PR #.

[matteius]

@agalazis Please add a news fragment, and thank you.

[Copilot]

Pull Request Overview

This PR corrects documentation for speeding up Pipenv installations by replacing the incorrect --pip-args flag with the correct --extra-pip-args flag in the Docker documentation example.

• Fixed incorrect command line argument in Docker installation example
• Updated documentation to use the proper --extra-pip-args flag instead of --pip-args

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