Fix remarks from #257 for release 2.5

[WackerO]

Fixes remarks from #257 by removing excessive check of the pathway_adj_pval_threshold param, adding a default description and prettifying

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).

[famosab]

I think the linting fails because of the nf-validation / nf-schema changes. That can either be addressed with a TEMPLATE update or we fix it manually by updating the subworkflows and switching to nf-schema.

[famosab]

LGTM -> there is just the linting fail but maybe that does not need to be tackled in this PR.

[WackerO]

The linting stuff is because the template is old :S I did not have time for a template update. Thanks Famke!