[deps]: Update rust Docker tag to v1.81

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
rust	stage	minor	1.76 -> 1.81
rust	final	minor	1.76 -> 1.81

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Configuration

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[bitwarden-bot]

Internal tracking:

• ID: SM-1412
• Link: https://bitwarden.atlassian.net/browse/SM-1412

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.23%. Comparing base (4238faf) to head (bedf914).
Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #948   +/-   ##
=======================================
  Coverage   58.23%   58.23%           
=======================================
  Files         197      197           
  Lines       13469    13469           
=======================================
  Hits         7844     7844           
  Misses       5625     5625           

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