Adapt pipeline for nextflow 26.04.4

[matrulda]

When testing the sequencing-report-service (currently being named to nextflow-runner-service), I noticed this error. It went Away when I downgraded to nextflow 25.10.2.

Syntax fixes are probably needed to support 26.04.4.

$ nextflow run \
  /home/matilda/workspace/sequencing-report-service/seqreports/main.nf \
  -config /home/matilda/workspace/sequencing-report-service/seqreports/nextflow.config \
  -profile singularity,dev,test \
  --hello /home/matilda/workspace/sequencing-report-service/tests/resources/foo_runfolder
Nextflow 26.04.6 is available - Please consider updating your version to it

 N E X T F L O W   ~  version 26.04.4

Launching `/home/matilda/workspace/sequencing-report-service/seqreports/main.nf` [elegant_lalande] revision: b2e2691c18

Error main.nf:97:44: Unexpected input: '$'
│  97 |                 [(file.toString() =~ /^.*\/${params.demultiplexer_outd
╰     |                                            ^
``