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

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v4 → v6

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Release Notes

actions/checkout (actions/checkout)

v6

Compare Source

v5

Compare Source

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[what-the-diff]

PR Summary

• Upgrade of the 'actions/checkout' component
  The 'actions/checkout' component, which the team uses across several workflow files, has been updated from version 4 to version 6. This improvement is expected to enhance the overall performance of these workflows (buddy-bot.yml, ci.yml, export-size.yml, release.yml).