Add Gaia v20.0.0 to chains running tests in CI

[ljoss17]

Closes: #XXX

Description

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PR author checklist:

• [ ] Added changelog entry, using unclog.
• [ ] Added tests: integration (for Hermes) or unit/mock tests (for modules).
• [ ] Linked to GitHub issue.
• [ ] Updated code comments and documentation (e.g., docs/).
• [ ] Tagged one reviewer who will be the one responsible for shepherding this PR.

Reviewer checklist:

• [ ] Reviewed Files changed in the GitHub PR explorer.
• [ ] Manually tested (in case integration/unit/mock tests are absent).