[ci] Roll pinned nightly toolchain

[google-pr-creation-bot]

Automated changes by create-pull-request GitHub action

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.38%. Comparing base (e112723) to head (1b294c6).
⚠️ Report is 269 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2462   +/-   ##
=======================================
  Coverage   90.38%   90.38%           
=======================================
  Files          18       18           
  Lines        7287     7287           
=======================================
  Hits         6586     6586           
  Misses        701      701           

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