chore(deps): bump h2 from 4.2.0 to 4.3.0

[dependabot]

Bumps h2 from 4.2.0 to 4.3.0.

Changelog

Sourced from h2's changelog.

4.3.0 (2025-08-23)

API Changes (Backward Incompatible)

• Reject header names and values containing illegal characters, based on RFC 9113, section 8.2.1. The main Python API is compatible, but some previously valid requests/response headers might now be blocked. Use the validate_inbound_headers config option if needed. Thanks to Sebastiano Sartor (sebsrt) for the report.
• Convert emitted events into Python dataclass, which introduces new constructors with required arguments. Instantiating these events without arguments, as previously commonly used API pattern, will no longer work.

API Changes (Backward Compatible)

• h2 events now have tighter type bounds, e.g. stream_id is guaranteed to not be None for most events now. This simplifies downstream type checking.
• Various typing-related improvements.

Bugfixes

• Fix error value when opening a new stream on too many open streams.

Commits

• 1aae569 v4.3.0
• 9e4bbed merge surrounding whitespace and uppercase validators into illegal character ...
• 035e989 be stricter about which characters to accept for headers
• 883ed37 reject header names and values containing unpermitted characters \r, \n, ...
• 0583911 lint: fix TC006
• bbd3d90 fix(packaging): bump twine to pass meta check wildcard bugs
• ea3140f cleanup
• 9ce83ff exclude RDT from sdist
• 492d3db Update .readthedocs.yaml
• 243461d Create RTD config
• Additional commits viewable in compare view

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