Update actions/checkout action to v6

This MR 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

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• 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

Compare Source

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

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