Bump actions/checkout to v6

[jbampton]

https://github.com/actions/checkout/releases/tag/v6.0.0

Description

This PR...

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)
• Build/CI
• Test (unit or integration test code)

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

• Major
• Minor

Bug Severity

• BLOCKER
• Critical
• Major
• Minor
• Trivial

Screenshots (if appropriate):

How Has This Been Tested?

How did you try to break this feature and the system with this change?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 17.57%. Comparing base (db61470) to head (0f7e15f).

Additional details and impacted files

@@            Coverage Diff            @@
##               main   #12164   +/-   ##
=========================================
  Coverage     17.56%   17.57%           
- Complexity    15548    15550    +2     
=========================================
  Files          5913     5913           
  Lines        529440   529440           
  Branches      64670    64670           
=========================================
+ Hits          93019    93030   +11     
+ Misses       425963   425950   -13     
- Partials      10458    10460    +2     

Flag	Coverage Δ
uitests	3.58% <ø> (ø)
unittests	18.63% <ø> (+<0.01%)	⬆️

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