fix create-test-yml

[KevinMenden]

Fix bug in nf-core modules create-test-yml that occurs when specifying the output directory.

Now the simply doesn't compare md5 sums when a output directory is specified. Otherwise we'd have to ask the user for two directories which gets a bit much. The best way is to run it without a specified directory anyway.

Fixes #1148

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 #1161 (6876b7e) into dev (5e9e33c) will increase coverage by 0.00%.
The diff coverage is 66.66%.

@@           Coverage Diff           @@
##              dev    #1161   +/-   ##
=======================================
  Coverage   69.22%   69.23%           
=======================================
  Files          50       50           
  Lines        5232     5233    +1     
=======================================
+ Hits         3622     3623    +1     
  Misses       1610     1610           

Impacted Files	Coverage Δ
nf_core/modules/test_yml_builder.py	45.98% <66.66%> (+0.29%)	⬆️

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[ErikDanielsson]

LGTM 👍