DM-38815: Add one more variable to set in set_thread_envvars

[andy-slac]

When set to "false" the envvar OMP_PROC_BIND should stop OpenMP from setting CPU affinity.

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 (7069b80) 93.62% compared to head (70e96a1) 93.63%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #157   +/-   ##
=======================================
  Coverage   93.62%   93.63%           
=======================================
  Files          43       43           
  Lines        2698     2702    +4     
=======================================
+ Hits         2526     2530    +4     
  Misses        172      172           

Impacted Files	Coverage Δ
python/lsst/utils/threads.py	84.00% <100.00%> (+2.18%)	⬆️
tests/test_threads.py	84.61% <100.00%> (+0.61%)	⬆️

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