Remove streamers from Kid Mode

Kid Mode accounts on the website cannot access lichess.org/streamer.

However, when using the app in Kid Mode, streamers are shown in the "Watch" tab (and can be expanded with "More >").

In order to align with the website, and to keep the promise made to guardians on https://lichess.org/account/kid, the "Streamers" section should be removed from the "Watch" tab in Kid Mode.