Update backports-zstd requirement from >=1.0.0 to >=1.6.0

[dependabot]

Updates the requirements on backports-zstd to permit the latest version.

Changelog

Sourced from backports-zstd's changelog.

1.6.0 - 2026-06-14

🚀 Added

• Update code with CPython 3.14.6 version

1.5.0 - 2026-05-11

🚀 Added

• Update code with CPython 3.14.5 version

1.4.0 - 2026-05-03

🚀 Added

• Update code with CPython 3.14.4 version
• Update type hints with typeshed 44dac88
• Remove support for CPython 3.9
• Build wheels for Android
• Build wheels for iOS
• Stop building wheels for CPython 3.13 free-threading

1.3.0 - 2025-12-29

🚀 Added

• Update type hints with typeshed bbddfee

🐛 Fixes

• Fix conflict on __init__.py file on backports root module by transforming backports.zstd into an implicit namespace package (see PEP-420)
• Raise an exception at both build and runtime when using an unsupported Python version, instead of crashing with a segmentation fault at runtime (in the rare cases where backports.zstd was installed despite the requires-python marker)

1.2.0 - 2025-12-06

🚀 Added

... (truncated)

Commits

• 7e15b44 chore: prepare v1.6.0
• ff653ad chore: port changes to CFFI implementation
• 7f4c31b feat: update code from upstream 3.14.6
• 63fd605 chore: prepare v1.5.0
• 0d39086 feat: update code from upstream 3.14.5
• 01db30f chore: prepare v1.4.0
• 583a808 chore: remove support for 3.9
• 09739b9 chore: add zizmor ci check
• f11c344 chore: update type hints from upstream
• c10804a feat: build Python 3.13 wheels for Android and iOS
• Additional commits viewable in compare view

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[sleepyStick]

i don't think we can do this one at the moment given that we still support python3.9:

[2026/07/24 12:23:29.072] Creating virtual environment at: .venv
[2026/07/24 12:23:29.072] × No solution found when resolving dependencies for split (markers:
[2026/07/24 12:23:29.072] │ python_full_version > '3.9' and python_full_version < '3.10'):
[2026/07/24 12:23:29.072] ╰─▶ Because only backports-zstd{python_full_version < '3.14'}<=1.6.0 is
[2026/07/24 12:23:29.072] available and the requested Python version (>=3.9) does not satisfy
[2026/07/24 12:23:29.072] Python>=3.10, we can conclude that backports-zstd{python_full_version <
[2026/07/24 12:23:29.072] '3.14'}>=1.6.0 cannot be used.
[2026/07/24 12:23:29.072] And because pymongo[zstd] depends on backports-zstd{python_full_version
[2026/07/24 12:23:29.072] < '3.14'}>=1.6.0 and your project requires pymongo[zstd], we can
[2026/07/24 12:23:29.072] conclude that your project's requirements are unsatisfiable.
[2026/07/24 12:23:29.072] hint: While the active Python version is 3.10, the resolution failed for
[2026/07/24 12:23:29.072] other Python versions supported by your project. Consider limiting your
[2026/07/24 12:23:29.072] project's supported Python versions using requires-python.