rust-toolchain: Update

[alexdewar]

Automatic change by the update-rust-toolchain Github Action.

Github Actions will not run workflows on pull requests which are opened by a GitHub Action.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.45%. Comparing base (ee3283e) to head (34dd3b6).
⚠️ Report is 1 commits behind head on fix-update-toolchain-workflow.

Additional details and impacted files

@@                      Coverage Diff                       @@
##           fix-update-toolchain-workflow    #1038   +/-   ##
==============================================================
  Coverage                          81.45%   81.45%           
==============================================================
  Files                                 52       52           
  Lines                               6497     6497           
  Branches                            6497     6497           
==============================================================
  Hits                                5292     5292           
  Misses                               949      949           
  Partials                             256      256           

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