Add Rust version to adaptive sampling documentation

[bm1549]

What does this PR do? What is the motivation?

Adds the supported version of adaptive sampling for Rust

Merge instructions

Pending release of dd-trace-rs v0.4.0

Merge readiness:

• Ready for merge

AI assistance

Fully manual

Additional notes

[github-actions]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/brian.marks/rust-sampling/tracing/trace_pipeline/adaptive_sampling

[joepeeples]

Pending release of dd-trace-rs v0.3.4 (does not exist yet)

@bm1549 Do you have an estimate of when the new version will be available? I'd rather approve this when we can verify the link will actually work (it returns 404 now).

[bm1549]

Pending release of dd-trace-rs v0.3.4 (does not exist yet)

@bm1549 Do you have an estimate of when the new version will be available? I'd rather approve this when we can verify the link will actually work (it returns 404 now).

@joepeeples it will be released this week

[joepeeples]

Approved to avoid blocking an imminent release, but please do not merge until you've confirmed the link resolves correctly. Thanks @bm1549!