Cleanup transition steps used to update test reports on main

[fab-10]

PR description

No that previous PR #7141 is merged and test reports are correctly updated when merging a PR on main branch, we can safely remove the steps that were added to support the transition.

This PR also increases the number of AT runners as a workaround for failing jobs, until we properly fix them.

Fixed Issue(s)

Thanks for sending a pull request! Have you done the following?

• [ ] Checked out our contribution guidelines?
• [ ] Considered documentation and added the doc-change-required label to this PR if updates are required.
• [ ] Considered the changelog and included an update if required.
• [ ] For database changes (e.g. KeyValueSegmentIdentifier) considered compatibility and performed forwards and backwards compatibility tests

Locally, you can run these tests to catch failures early:

• [ ] unit tests: ./gradlew build
• [ ] acceptance tests: ./gradlew acceptanceTest
• [ ] integration tests: ./gradlew integrationTest
• [ ] reference tests: ./gradlew ethereum:referenceTests:referenceTests