Linting params in main.nf

[asp8200]

#2833. Trying to only match assignments of params in main.nf and not references like, for instance, params.aligner == "bwa-mem".

I tested this solution locally on this version of Sarek.

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

[mirpedrol]

LGTM :)