deps(renovate): 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

Compare Source

v5

Compare Source

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 93.97%. Comparing base (8dd27c1) to head (c8cded0).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #383   +/-   ##
=======================================
  Coverage   93.97%   93.97%           
=======================================
  Files           3        3           
  Lines         166      166           
  Branches       42       42           
=======================================
  Hits          156      156           
  Misses          7        7           
  Partials        3        3           

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