Stabilize booktests in vinberg

[HechtiDerLachs]

This is an attempt to hopefully stabilize the booktests; see #4493.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.33%. Comparing base (ae6f43f) to head (fde7fdf).
Report is 9 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4766      +/-   ##
==========================================
- Coverage   84.57%   84.33%   -0.25%     
==========================================
  Files         674      675       +1     
  Lines       90802    91066     +264     
==========================================
+ Hits        76798    76801       +3     
- Misses      14004    14265     +261     

Files with missing lines	Coverage Δ
.../AlgebraicGeometry/Schemes/Sheaves/IdealSheaves.jl	81.03% <100.00%> (-0.38%)	⬇️

... and 4 files with indirect coverage changes

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[thofma]

For the sake of our sanity upstream, I will mark this to be backported. (In case we will have another 1.3.* release before 1.4.)

[HechtiDerLachs]

@simonbrandhorst : Could you maybe approve this? I did not change any mathematics, only the algorithmic path to get to our results. Feel free to contact me on Slack if in doubt.