Allow external contributors to run E2E

[xandervedder]

          Might be a separate issue, but external contributors can't run e2e tests in CI: https://github.com/stryker-mutator/stryker-dashboard/actions/runs/8323453511/job/22773317305

Originally posted by @hugo-vrijswijk in #550 (comment)

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It is possible that some access tokens are not present when running, thus it fails.