Use golangci-lint directive for workflow deprecation warning

What does this MR do and why?

Problem

golangci-lint v2 ignored the native //lint:ignore SA1019 directive, so the deprecated WorkflowDefinition warning remained active and was masked by a stale acceptable-warning entry.

Solution

• Replace the ineffective directive with //nolint:staticcheck.
• Remove the redundant SA1019 entry from the acceptable-warnings file.

How to set up and validate locally

1. Run cd workhorse && make lint.

MR acceptance checklist

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