Enable allow-parallel-runners in golangci-lint config

[denik]

Summary

• Adds allow-parallel-runners: true under the run section in .golangci.yaml to permit parallel test runner execution with golangci-lint.

Test plan

• Verify make lint still passes

This pull request was AI-assisted by Isaac.

[github-actions]

Waiting for approval

Based on git history, these people are best suited to review:

• @pietern -- recent work in ./

Eligible reviewers: @andrewnester, @anton-107, @renaudhartert-db, @shreyas-goenka, @simonfaltum

_{Suggestions based on git history. See OWNERS for ownership rules.}