chore(deps): update actions/checkout action to v6

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v3 → v6

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Release Notes

actions/checkout (actions/checkout)

v6

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v5

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v4

Compare Source

• url-helper.ts now leverages well-known environment variables by @​jww3 in #​1941
• Expand unit test coverage for isGhes by @​jww3 in #​1946

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Configuration

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.07%. Comparing base (7676848) to head (9730c3a).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #143      +/-   ##
==========================================
+ Coverage   85.95%   86.07%   +0.12%     
==========================================
  Files          11       11              
  Lines        4457     4461       +4     
==========================================
+ Hits         3831     3840       +9     
+ Misses        626      621       -5     

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