show dmr label for version select in archived docs

[ran-huang]

Show a (DMR) label for DMR versions like this: (only applicable to archived docs)

[vercel[bot]]

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Name	Status	Preview	Comments	Updated (UTC)
website-docs	❌ Failed (Inspect)			Jul 26, 2023 8:40am

[vercel[bot]]

@ran-huang is attempting to deploy a commit to the pingcap Team on Vercel.

A member of the Team first needs to authorize it.