ci: improve rust-version check

[rnbguy]

Closes: #1382

Description

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PR author checklist:

• Added changelog entry, using unclog.
• Added tests.
• Linked to GitHub issue.
• Updated code comments and documentation (e.g., docs/).
• Tagged one reviewer who will be the one responsible for shepherding this PR.

Reviewer checklist:

• Reviewed Files changed in the GitHub PR explorer.
• Manually tested (in case integration/unit/mock tests are absent).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.83%. Comparing base (0357976) to head (356e592).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1381   +/-   ##
=======================================
  Coverage   66.83%   66.83%           
=======================================
  Files         225      225           
  Lines       22594    22594           
=======================================
  Hits        15100    15100           
  Misses       7494     7494           

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[rnbguy]

build still fails as the latest tendermint-proto and scale-info pulls the latest parity-scale-codec.