Update aws megatests GH actions

[ggabernet]

nf-core/sarek pull request

Fix --outdir param

PR checklist

• This comment contains a description of changes (with reason)
• If you've fixed a bug or added code that should be tested, add tests!
• If necessary, also make a PR on the nf-core/sarek branch on the nf-core/test-datasets repo
• Ensure the test suite passes (nextflow run . -profile test,docker).
• Make sure your code lints (nf-core lint .).
• Documentation in docs is updated
• CHANGELOG.md is updated
• README.md is updated

Learn more about contributing: CONTRIBUTING.md

[maxulysse]

I think you still have issues with the credentials

[ggabernet]

https://github.com/nf-core/sarek/settings/secrets

So it seems like secrets are not passed to pull requests, so we would need to merge to fully test it.
It also makes sense, as otherwise, anyone making a PR could use our secrets for testing :)