linting tests requiring nf-test will be warnings instead of failures

[mirpedrol]

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

[codecov]

Codecov Report

Attention: 18 lines in your changes are missing coverage. Please review.

Comparison is base (2720bf9) 74.58% compared to head (3a556d0) 74.50%.

Files	Patch %	Lines
nf_core/modules/lint/module_tests.py	47.05%	9 Missing ⚠️
nf_core/subworkflows/lint/subworkflow_tests.py	43.75%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #2524      +/-   ##
==========================================
- Coverage   74.58%   74.50%   -0.08%     
==========================================
  Files          85       85              
  Lines        9147     9167      +20     
==========================================
+ Hits         6822     6830       +8     
- Misses       2325     2337      +12     

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[asp8200]

I need this

[pinin4fjords]

Yes please!