chore(deps): bump greenlet from 3.3.2 to 3.4.0

[dependabot]

Bumps greenlet from 3.3.2 to 3.4.0.

Changelog

Sourced from greenlet's changelog.

3.4.0 (2026-04-08)

• Publish binary wheels for RiscV 64.

• Fix multiple rare crash paths during interpreter shutdown.

  Note that this now relies on the atexit module, and introduces subtle API changes during interpreter shutdown (for example, getcurrent is no longer available once the atexit callback fires).

  See PR [#499](https://github.com/python-greenlet/greenlet/issues/499) <https://github.com/python-greenlet/greenlet/pull/499>_ by Nicolas Bouvrette.

• Address the results of an automated code audit performed by Daniel Diniz. This includes several minor correctness changes that theoretically could have been crashing bugs, but typically only in very rare circumstances.

  See PR 502 <https://github.com/python-greenlet/greenlet/pull/502>_.

• Fix several race conditions that could arise in free-threaded builds when using greenlet objects from multiple threads, some of which could lead to assertion failures or interpreter crashes.

  See issue 503 <https://github.com/python-greenlet/greenlet/issues/503>_, with thanks to Nitay Dariel and Daniel Diniz.

Commits

• df6734e Preparing release 3.4.0
• 0f86075 Merge pull request #504 from python-greenlet/freethreading-fixes
• 4596574 TLBC: crash appears to still happen on CI 3.14t ubuntu. Re-enable workaround.
• 2f4a1cf Make green_switch (python level greenlet.switch) and green_throw check for (p...
• a0c2a2a Fix unused variable warning when asserts are disabled.
• 8688581 gcc was complaining about an incomplete std::atomic type. make sure we includ...
• 449c760 Make MainGreenlet._thread_state atomic; we use it for cross thread checking a...
• f840e00 Add critical sections to greenlet attribute accessors.
• 6b281d3 test_contextvars: No need for the fallback case where contextvars isn't avail...
• f52615a Merge pull request #502 from python-greenlet/devdanzin-audit
• Additional commits viewable in compare view

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