Fix compatibility issue (release-7.1).

[RenxuanW]

New added field should be the last in serializer. #7095 in main.

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[foundationdb-ci]

AWS CodeBuild CI Report for macOS BigSur 11.5.2

• CodeBuild project: foundationdb-pr-macos
• Commit ID: 1bd1124
• Result: SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)

[fdb-windows-ci]

Doxense CI Report for Windows 10

• Commit ID: 1bd1124
• Result: ✔️ SUCCEEDED
• Build Logs (available for 30 days)

[foundationdb-ci]

AWS CodeBuild CI Report for Linux CentOS 7

• CodeBuild project: foundationdb-pr
• Commit ID: 1bd1124
• Result: SUCCEEDED
• Error: N/A
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