Use latest nf-schema 2.7.0

[apeltzer]

Description of feature

Please also make sure to update the pipeline usage of nf-schema to use 2.7.0 - and fix potential linting errors arising from that. This ensures we're 100% strict syntax compliant.

https://github.com/nextflow-io/nf-schema/releases/tag/2.7.0

[atrigila]

Additionally to fix:
https://github.com/nf-core/strict-syntax-health/blob/main/lint_results/prints-help-results/demultiplex_help.txt

[atrigila]

This should be done after bumping modules / subworkflows