fix(ci): revert to a previous async-nats version

[pront]

Summary

Reverted async-nats bump and tests are now passing.

Follow up: Need to ensure that the IT suite runs when dependencies change.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Checklist

• Please read our Vector contributor resources.
  • make check-all is a good command to run locally. This check is
    defined here. Some of these
    checks might not be relevant to your PR. For Rust changes, at the very least you should run:
    • cargo fmt --all
    • cargo clippy --workspace --all-targets -- -D warnings
    • cargo nextest run --workspace (alternatively, you can run cargo test --all)
• If this PR introduces changes Vector dependencies (modifies Cargo.lock), please
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References

Ref: #22242 (comment)

[pront]

/ci-run-integration-all

[pront]

/ci-run-integration-nats

[pront]

/ci-run-integration-nats

[pront]

• Failed: https://github.com/vectordotdev/vector/actions/runs/13138215406/job/36658665492?pr=22359
• Reverted async-nats, passed: https://github.com/vectordotdev/vector/actions/runs/13142717182/job/36673491467?pr=22359

[datadog-vectordotdev]

Datadog Report

Branch report: pront/test-nats-int-tests
Commit report: a0a69b2
Test service: vector

✅ 0 Failed, 7 Passed, 0 Skipped, 25.46s Total Time