Simplify Metadata errors

[Zethson]

• Simplify Metadata errors
• Remove slow mark

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.22%. Comparing base (8ffc29f) to head (0394a4a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #765   +/-   ##
=======================================
  Coverage   72.21%   72.22%           
=======================================
  Files          47       47           
  Lines        5449     5447    -2     
=======================================
- Hits         3935     3934    -1     
+ Misses       1514     1513    -1     

Files with missing lines	Coverage Δ
pertpy/__init__.py	100.00% <100.00%> (ø)
pertpy/data/_dataloader.py	100.00% <ø> (ø)
pertpy/metadata/_cell_line.py	52.09% <ø> (ø)
pertpy/metadata/_compound.py	70.73% <100.00%> (ø)
pertpy/metadata/_look_up.py	8.90% <ø> (ø)
pertpy/metadata/_metadata.py	60.86% <ø> (ø)
pertpy/metadata/_moa.py	74.41% <ø> (ø)
pertpy/tools/_augur.py	88.76% <ø> (-0.05%)	⬇️
pertpy/tools/_mixscape.py	82.68% <ø> (+0.35%)	⬆️

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