Make nominal_length and nominal_sdev optional in experiments

[ZuzanaSebb]

Hi @misialq,

I’ve removed nominal_length and nominal_sdev from the mandatory experiment parameters, in line with the SRA XML schema.

I updated library.py and test_library.py accordingly.

Regarding the provided experiment templates, I only modified experiment_minimal.tsv to reflect these changes. The extended templates for single and paired reads remain unchanged. The minimal template uses paired reads by default, so users can follow it without specifying nominal_length or nominal_sdev.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.13%. Comparing base (bc68788) to head (6cd2124).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #26      +/-   ##
==========================================
+ Coverage   95.07%   95.13%   +0.05%     
==========================================
  Files          27       27              
  Lines        1788     1808      +20     
==========================================
+ Hits         1700     1720      +20     
  Misses         88       88              

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[misialq]

Hey @ZuzanaSebb, thanks for the updates - LGTM! 🔥