DM-38469: Remove read_quantum_graph method.

[MichelleGower]

Call QuantumGraph.loadUri() directly as passing of butler repository's DimensionUniverse is no longer needed.

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Patch coverage: 40.00% and project coverage change: +0.10 🎉

Comparison is base (d08cb7c) 78.55% compared to head (1cd7976) 78.65%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #137      +/-   ##
==========================================
+ Coverage   78.55%   78.65%   +0.10%     
==========================================
  Files          39       39              
  Lines        2872     2863       -9     
  Branches      490      489       -1     
==========================================
- Hits         2256     2252       -4     
+ Misses        540      535       -5     
  Partials       76       76              

Impacted Files	Coverage Δ
python/lsst/ctrl/bps/pre_transform.py	46.05% <0.00%> (+1.47%)	⬆️
python/lsst/ctrl/bps/quantum_clustering_funcs.py	99.20% <ø> (ø)
python/lsst/ctrl/bps/clustered_quantum_graph.py	56.54% <50.00%> (-0.52%)	⬇️

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