DM-33140: Change log warning to debug

[mfisherlevine]

Checklist

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

[codecov]

Codecov Report

Merging #625 (c819404) into main (679b36c) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #625   +/-   ##
=======================================
  Coverage   84.08%   84.08%           
=======================================
  Files         237      237           
  Lines       30014    30014           
  Branches     4990     4990           
=======================================
  Hits        25238    25238           
  Misses       3638     3638           
  Partials     1138     1138           

Impacted Files	Coverage Δ
python/lsst/daf/butler/_butler.py	81.10% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 679b36c...c819404. Read the comment docs.