Creating a public room incorrectly enables encryption by default

**To Reproduce**
Steps to reproduce the behavior:
1. Click the + button
2. Create a new room
3. Tap Public room

The encryption toggle stays on

**Expected behavior**
In Element web and Android encryption is disabled by default when creating a public room

**Screenshots**

Version 1.4.1

Start by reproducing the issue in the iOS app's new-room flow: tap +, create a room, and select Public room. Compare the encryption toggle with the reported Element web and Android behavior; done means the toggle is disabled by default for public rooms.

Written by the indexing model from the issue text.