Prepare release v279

[heroku-linguist]

Commits since the last release:

• Stop installing pip into Poetry's virtual environment (Stop installing pip into Poetry's virtual environment #1761)
• Misc Poetry cleanups (Misc Poetry cleanups #1762)
• Migrate to Rubocop's new plugin syntax (Migrate to Rubocop's new plugin syntax #1763)
• Improve package manager bootstrap error messages (Improve package manager bootstrap error messages #1764)
• Stop filtering out pip's "Requirement already satisfied" log lines (Stop filtering out pip's "Requirement already satisfied" log lines #1765)
• Bump poetry from 2.0.1 to 2.1.1 (Bump poetry from 2.0.1 to 2.1.1 #1758)

For the full diff, see the compare view:
v278...main

[edmorley]

$ make publish
Checking environment...
Checking buildpack versions in sync...
Extracting changelog entry for this release...

- Updated Poetry from 2.0.1 to 2.1.1. ([#1758](https://github.com/heroku/heroku-buildpack-python/pull/1758))
- Stopped filtering out pip's `Requirement already satisfied:` log lines when installing dependencies. ([#1765](https://github.com/heroku/heroku-buildpack-python/pull/1765))
- Improved the error messages shown if installing pip/Poetry/Pipenv fails. ([#1764](https://github.com/heroku/heroku-buildpack-python/pull/1764))
- Stopped installing pip into Poetry's virtual environment. ([#1761](https://github.com/heroku/heroku-buildpack-python/pull/1761))

Deploy as v279 [y/n]? y

Creating GitHub release...
https://github.com/heroku/heroku-buildpack-python/releases/tag/v279

Publishing to the Heroku Buildpack Registry...
Two-factor code: ********************************************
Publishing buildpack heroku/python... done
Publishing buildpack was successful

 Version Released At              Status    
 ─────── ──────────────────────── ───────── 
 279     2025-02-26T08:43:02.082Z published