fix: text widget in dashboard to explain the lack of replica lag metric (#1698)

Looks like this:

<img width="1349" alt="Screenshot 2025-04-18 at 11 14 38 AM"
src="https://github.com/user-attachments/assets/f895170c-7953-4212-a1bc-72638219cca0"
/>


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under the terms of the Apache-2.0 license*

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Author: kaizencc