[Poll] - Add a description under undisclosed poll when not ended

[mnaturel]

Your use case

What would you like to do?

Add a description "Results will be visible when the poll is ended" under undisclosed and not ended poll.

Why would you like to do it?

To provide some information to the user.

How would you like to achieve it?

Add a new String and update the corresponding ViewState.

Have you considered any alternatives?

No response

Additional context

No response

Are you willing to provide a PR?

Yes