fix: pin cryptography<46 for PyPy 3.10 CI builds

[WilliamBergamin]

Summary

These changes aim to fix the CI by pinning cryptography<46 for PyPy 3.10 via environment markers

• cryptography 46+ uses PyO3 0.27+, which dropped PyPy 3.10 support, causing the source build to fail with: error: the configured PyPy interpreter version (3.10) is lower than PyO3's minimum supported version (3.11)
• cryptography 45.0.x is the last version with pre-built PyPy 3.10 wheels

Testing

CI tests should be sufficient

Category

• slack_sdk.web.WebClient (sync/async) (Web API client)
• slack_sdk.webhook.WebhookClient (sync/async) (Incoming Webhook, response_url sender)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.signature (Request Signature Verifier)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.models (UI component builders)
• slack_sdk.scim (SCIM API client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.rtm_v2 (RTM client)
• /docs (Documents)
• /tutorial (PythOnBoardingBot tutorial)
• tests/integration_tests (Automated tests for this library)

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run python3 -m venv .venv && source .venv/bin/activate && ./scripts/run_validation.sh after making the changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.01%. Comparing base (aa3a16d) to head (6c53691).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1860   +/-   ##
=======================================
  Coverage   84.01%   84.01%           
=======================================
  Files         117      117           
  Lines       13256    13256           
=======================================
  Hits        11137    11137           
  Misses       2119     2119           

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[srtaalej]

thanks for updating this!