ci: add DCO to the Scala Steward configuration

[yshyn-iohk]

Description:

Summarize the changes you're submitting in a few sentences, including Jira ticket ATL-xxxx if applicable.
Link to any discussion, related issues, and bug reports to give the context and help the reviewer understand the PR.

Checklist:

• My PR follows the contribution guidelines of this project
• My PR is free of third-party dependencies that don't comply with the Allowlist
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked the PR title to follow the conventional commit specification

[github-actions]

Integration Test Results

 5 files   5 suites   11s ⏱️
17 tests 17 ✅ 0 💤 0 ❌
20 runs  20 ✅ 0 💤 0 ❌

Results for commit baf1464.

[FabioPinheiro]

Thanks