Rebrand: confirm the "DocumentDB" display name on the Marketplace (operator) #1026

Part of #1024. Step 2, blocks the displayName change.

The Marketplace rejects a displayName that another extension already uses, and "DocumentDB" is also the platform name.

• Confirm that ms-azuretools.vscode-documentdb can publish with "displayName": "DocumentDB" (pre-release or private test publish, or with the Marketplace team).
• If it is not accepted, agree on a fallback short name and update the naming rule in the parent issue before the code change lands.