chore(huey): drop transaction based tracing

[pnagre05]

Description

I removed the transaction-based tracing fallback from the Huey integration - I did this by doing the following:

• Removed all has_span_streaming_enabled branching and enforced the use of sentry_sdk.traces.start_span for both patch_enqueue and patch_execute
• Removed legacy compatibility utilities like the else: fallback blocks and the legacy continue_trace/set_status calls on scope.transaction
• Deleted transaction-based tests (like the has_span_streaming parameterization) and updated the remaining test suite to unconditionally validate span streaming payloads instead of legacy transactions

Issues

• resolves: Remove transaction-based tracing from huey #7095

Reminders

• Please add tests to validate your changes, and lint your code using uv run ruff.
• Add GH Issue ID & Linear ID (if applicable)
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

[sentrivana]

Hey @pnagre05, thanks for this one, too. It looks great, just two minor comments. I'll also run CI on it.

Thanks especially for migrating the tests that we apparently had forgotten about when adding span streaming to this integration, like test_huey_enqueue.