Fix for flaky test

[cmdcolin]

Possible fix for #3260

This fix creates a small minimal config for testing the wrong assembly error

A possible alternative to this approach would be checking that the LGV is initialized before finishing test, but I think the minimal config would not try to load any refnamealiases and thus would not cause any error

[codecov]

Codecov Report

Merging #3261 (4a32fbd) into main (1b3cd83) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #3261      +/-   ##
==========================================
+ Coverage   59.45%   59.47%   +0.02%     
==========================================
  Files         676      676              
  Lines       28823    28823              
  Branches     7038     7038              
==========================================
+ Hits        17137    17143       +6     
+ Misses      11412    11406       -6     
  Partials      274      274              

Impacted Files	Coverage Δ
packages/core/assemblyManager/assembly.ts	90.13% <100.00%> (ø)
...rative-view/src/ServerSideRenderedBlockContent.tsx	64.00% <0.00%> (-4.00%)	⬇️
products/jbrowse-web/src/util.ts	48.33% <0.00%> (ø)
packages/core/util/layouts/GranularRectLayout.ts	87.28% <0.00%> (+0.42%)	⬆️
...FeatureRenderer/components/ProcessedTranscript.tsx	88.73% <0.00%> (+1.40%)	⬆️
...gins/svg/src/SvgFeatureRenderer/components/util.ts	95.91% <0.00%> (+4.08%)	⬆️
...src/SvgFeatureRenderer/components/FeatureLabel.tsx	82.50% <0.00%> (+5.00%)	⬆️
...svg/src/SvgFeatureRenderer/components/Segments.tsx	92.85% <0.00%> (+7.14%)	⬆️

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