Fix malformed parameters declaration in set-dry-run.yml

[lbussell]

Summary

Fixes a malformed parameters: declaration in eng/docker-tools/templates/steps/set-dry-run.yml.

The block used YAML map syntax:

parameters:
  name: publishConfig
  type: object

Azure Pipelines interprets this as defining two parameters named name and type rather than a single publishConfig parameter. This breaks the caller (templates/jobs/publish.yml), which passes publishConfig, and causes the in-template ${{ parameters.publishConfig.PublishRegistry.repoPrefix }} reference to fail.

The fix uses the standard typed-list syntax used throughout the other templates:

parameters:
- name: publishConfig
  type: object

Context

This addresses the issue raised in #2159 (comment). PR #2159 moves the eng/docker-tools directory, but per request the fix is applied at the source-of-truth location under eng/docker-tools instead.

Validation

• Confirmed the corrected syntax matches sibling step templates (e.g. reference-service-connections.yml, run-imagebuilder.yml).
• Confirmed the only caller (templates/jobs/publish.yml) passes publishConfig.
• Non-breaking change (restores intended behavior); no CHANGELOG entry required.