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

[kjoremiljo-renovate]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v5.0.0 -> v6.0.2

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Release Notes

actions/checkout (actions/checkout)

v6.0.2

Compare Source

• Fix tag handling: preserve annotations and explicit fetch-tags by @​ericsciple in #​2356

v6.0.1

Compare Source

• Add worktree support for persist-credentials includeIf by @​ericsciple in #​2327

v6.0.0

Compare Source

• Persist creds to a separate file by @​ericsciple in #​2286
• Update README to include Node.js 24 support details and requirements by @​salmanmkc in #​2248

v5.0.1

Compare Source

• Port v6 cleanup to v5 by @​ericsciple in #​2301

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