Handle Superchain Registry removed chains

[emlautarom1]

Description
When a chain is removed from the Superchain Registry tests in the Nethermind.Runner.Test project can fail due to "Dictionary mismatch".

Steps to Reproduce

1. Include some chain x-l1 in the Superchain Registry
2. Run our action to generate and update Superchain configs: https://github.com/NethermindEth/nethermind/actions/workflows/update-superchain.yml
3. Merge the generated configs
4. Delete the chain x-l1 from the Superchain Registry
5. Run the Nethermind.Runner.Test project.

Actual behavior
The test suite fails due to a "Dictionary Mismatch"

Expected behavior
There should be no errors, and tests should continue to work.

Additional context
This issue has showed up recently in these workflows:

• https://github.com/NethermindEth/nethermind/actions/runs/19536386252/job/55931469448?pr=9560#step:4:80
• https://github.com/NethermindEth/nethermind/actions/runs/19603385533/job/56139193780?pr=9757