DM-39751: Clarify where a warning comes from and hide it

[timj]

Checklist

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

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (c31cead) 88.01% compared to head (34ac16c) 88.01%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #854   +/-   ##
=======================================
  Coverage   88.01%   88.01%           
=======================================
  Files         269      269           
  Lines       35417    35423    +6     
  Branches     7423     7424    +1     
=======================================
+ Hits        31173    31179    +6     
  Misses       3103     3103           
  Partials     1141     1141           

Impacted Files	Coverage Δ
python/lsst/daf/butler/registries/sql.py	85.07% <100.00%> (+0.08%)	⬆️
.../butler/registry/datasets/byDimensions/_manager.py	93.65% <100.00%> (+0.03%)	⬆️
...ython/lsst/daf/butler/registry/obscore/_manager.py	82.65% <100.00%> (+0.10%)	⬆️
...ython/lsst/daf/butler/registry/obscore/_records.py	82.64% <100.00%> (+0.14%)	⬆️

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[andy-slac]

Looks good