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 90.52%. Comparing base (0aacf50) to head (2a0f937).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #402   +/-   ##
=======================================
  Coverage   90.52%   90.52%           
=======================================
  Files         144      144           
  Lines        2196     2196           
  Branches      452      476   +24     
=======================================
  Hits         1988     1988           
+ Misses        200      197    -3     
- Partials        8       11    +3     

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