DM-33174: Allow "@" in run collection names

[timj]

They were not included in the none-magic list of characters.

Checklist

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

[codecov]

Codecov Report

Merging #627 (b629eb9) into main (b8699d7) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #627   +/-   ##
=======================================
  Coverage   84.09%   84.09%           
=======================================
  Files         237      237           
  Lines       30023    30027    +4     
  Branches     4989     4989           
=======================================
+ Hits        25247    25251    +4     
  Misses       3638     3638           
  Partials     1138     1138           

Impacted Files	Coverage Δ
python/lsst/daf/butler/core/utils.py	88.88% <100.00%> (ø)
tests/test_butler.py	97.63% <100.00%> (+<0.01%)	⬆️

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[andy-slac]

Looks great.