[stable29] feat(files): increase max copy-move concurrency to 5

[backportbot[bot]]

Backport of #46127

Warning, This backport's changes differ from the original and might be incomplete ⚠️

Todo

• [ ] Review and resolve any conflicts

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[nfebe]

/compile