DM-41570: Update imports for new location of SqlRegistry class

[andy-slac]

Checklist

• added documentation for a new migration script

[codecov-commenter]

Codecov Report

Attention: 13 lines in your changes are missing coverage. Please review.

Comparison is base (6f53698) 55.96% compared to head (baadca2) 55.90%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
- Coverage   55.96%   55.90%   -0.07%     
==========================================
  Files          32       32              
  Lines        1106     1109       +3     
  Branches      254      178      -76     
==========================================
+ Hits          619      620       +1     
- Misses        453      455       +2     
  Partials       34       34              

Files	Coverage Δ
python/lsst/daf/butler_migrate/registry.py	75.00% <66.66%> (ø)
...f/butler_migrate/script/rewrite_sqlite_registry.py	20.20% <25.00%> (+0.41%)	⬆️

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