Fixed bug with github actions

[WackerO]

Updates actions/upload-artifact to v4 to fix a CI bug

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 you've added a new tool - have you followed the pipeline conventions in the contribution docs
• Make sure your code lints (nf-core lint).
• Ensure the test suite passes (nextflow run . -profile test,docker --outdir <OUTDIR>).
• Usage Documentation in docs/usage.md is updated.
• Output Documentation in docs/output.md is updated.
• CHANGELOG.md is updated.
• README.md is updated (including new tool citations and authors/contributors).

[d4straub]

LGTM, I assume the template isnt at 3.0.2 and the failing nf-core linting / nf-core (pull_request) is therefore to be ignored?

[WackerO]

Hey Daniel, thanks for the review! Yes, the template is quite behind...