add tests for subworkflows install command

[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

Merging #1996 (36df3fb) into dev (d325e69) will decrease coverage by 0.22%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##              dev    #1996      +/-   ##
==========================================
- Coverage   63.37%   63.15%   -0.23%     
==========================================
  Files          44       43       -1     
  Lines        5030     4951      -79     
==========================================
- Hits         3188     3127      -61     
+ Misses       1842     1824      -18     

Impacted Files	Coverage Δ
nf_core/components/components_install.py	80.70% <50.00%> (+11.05%)	⬆️
nf_core/subworkflows/install.py

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[mirpedrol]

@nf-core-bot fix linting