[deps]: Update actions/checkout action to v6

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v5.0.1 -> v6.0.0

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Release Notes

actions/checkout (actions/checkout)

v6.0.0

Compare Source

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Configuration

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[bitwarden-bot]

Internal tracking:

• ID: PM-28930
• Link: https://bitwarden.atlassian.net/browse/PM-28930

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.60%. Comparing base (3c660ea) to head (b012b5c).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #17715   +/-   ##
=======================================
  Coverage   41.60%   41.60%           
=======================================
  Files        3553     3553           
  Lines      102390   102390           
  Branches    15366    15366           
=======================================
+ Hits        42595    42602    +7     
+ Misses      58002    57995    -7     
  Partials     1793     1793           

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