Update actions/checkout action to v7

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v6 → v7

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Release Notes

actions/checkout

v7.0.1

Compare Source

• Skip running unsafe pr check if input is default by @​aiqiaoy in #​2518
• Trim only ascii whitespace for branch by @​aiqiaoy in #​2521
• Escape values passed to --unset by @​aiqiaoy in #​2530
• Various dependency updates

v7.0.0

Compare Source

• Block checking out fork PR for pull_request_target and workflow_run by @​aiqiaoy in #​2454
• Various dependency updates

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