remove assert and code cleanup

[fabianegli]

This PR removes all assert statements from production code.

It also contains minuscule code cleanup and speedups.

Closes #1533

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 #1685 (4787815) into dev (cc1ab61) will decrease coverage by 0.24%.
The diff coverage is 62.71%.

@@            Coverage Diff             @@
##              dev    #1685      +/-   ##
==========================================
- Coverage   67.99%   67.74%   -0.25%     
==========================================
  Files          56       56              
  Lines        6609     6654      +45     
==========================================
+ Hits         4494     4508      +14     
- Misses       2115     2146      +31     

Impacted Files	Coverage Δ
nf_core/__main__.py	52.95% <12.50%> (+0.59%)	⬆️
nf_core/lint/multiqc_config.py	66.66% <50.00%> (-14.59%)	⬇️
nf_core/lint/readme.py	75.75% <50.00%> (-4.89%)	⬇️
nf_core/utils.py	80.32% <50.00%> (+0.20%)	⬆️
nf_core/launch.py	63.93% <62.50%> (-0.41%)	⬇️
nf_core/lint/actions_awsfulltest.py	83.33% <66.66%> (-5.56%)	⬇️
nf_core/schema.py	75.88% <69.76%> (-1.51%)	⬇️
nf_core/lint/actions_awstest.py	78.94% <75.00%> (-4.39%)	⬇️
nf_core/lint/actions_ci.py	85.48% <78.57%> (-3.61%)	⬇️
nf_core/lint/nextflow_config.py	77.45% <85.71%> (-0.11%)	⬇️
... and 3 more

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[ErikDanielsson]

Looks good to me! The changelog needs updating before we merge though.

[ErikDanielsson]

Looks good, just a typo.