Update actions/checkout action to v6

[red-hat-konflux]

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

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

v5

Compare Source

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

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