build(deps): update greenlet requirement from >=3.0 to >=3.5.5 in /backend

[dependabot]

Updates the requirements on greenlet to permit the latest version.

Changelog

Sourced from greenlet's changelog.

3.5.5 (2026-08-10)

• Link the C++ runtime statically into the Windows wheels again, as the Appveyor builds did through 3.3.0. Since 3.3.1 _greenlet.pyd imported MSVCP140.dll, which no Windows CPython distribution ships, so importing greenlet failed on machines without the Visual C++ redistributable. See issue 525 <https://github.com/python-greenlet/greenlet/issues/525>_. Issue and pull request by Daniel Sticker.

.. note:: Binary 3.15 wheels are now built with 3.15.0rc1. This should be compatible with future 3.15 releases and is believed compatible with 3.15b4 as well (but not earlier versions).

3.5.4 (2026-07-22)

• Fix a crash (segfault) on free-threaded builds of Python 3.14 and later when the garbage collector runs while a greenlet that was started from a non-empty C-stack-reference state is active. See issue 515 <https://github.com/python-greenlet/greenlet/issues/515>_. Thanks to ddorian and Kumar Aditya.

• Fix a potential use-after-free on free-threaded builds of Python 3.14 and later when the garbage collector runs while a greenlet is suspended holding a _PyCStackRef (for example, mid attribute resolution). See issue 515 <https://github.com/python-greenlet/greenlet/issues/515>_. Thanks to ddorian and Kumar Aditya.

• Fix a deadlock on free-threaded builds when a greenlet switch happened while a PyCriticalSection was held -- for example inside asyncio's Task.__step, which holds one on the running task for the duration of the step. See PR 519 <https://github.com/python-greenlet/greenlet/pull/519/>. Thanks to ddorian and Kumar Aditya.

.. note:: Binary 3.15 wheels are now built with Python 3.15b4. These may not be compatible with earlier or later versions of 3.15. Binary 3.15 wheels of greenlet from previous releases (e.g., 3.5.3) may not be compatible with Python 3.15b4.

3.5.3 (2026-06-26)

... (truncated)

Commits

• ddb1453 Preparing release 3.5.5
• 7de515c Update CHANGES: Credit for issue 525 and note about 3.15 binary wheels [skip ci]
• f3746aa Merge pull request #526 from stickerdaniel/windows-static-runtime
• f1ce3ca Restore static linking of the C++ runtime for Windows wheels
• b6690a5 Merge pull request #523 from python-greenlet/dependabot/github_actions/github...
• 726cc38 Bump the github-actions group with 3 updates
• e5c5f4c Merge pull request #522 from ddorian/c-stack-refs-test-detection
• be55a59 Check that the suspended greenlet is what keeps the class alive
• e9c01dd Back to development: 3.5.5
• 384be88 Preparing release 3.5.4
• Additional commits viewable in compare view

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