[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 90.36%. Comparing base (ec3f993) to head (6f692eb).
⚠️ Report is 240 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2499   +/-   ##
=======================================
  Coverage   90.36%   90.36%           
=======================================
  Files          19       19           
  Lines        7808     7808           
=======================================
  Hits         7056     7056           
  Misses        752      752           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.