[Developer mode] Able to change room's guest access with private visibility

In developer mode, we are able to change the public room's guest access setting (ie. the setting is only visible if room access is public).
If we change the visibility of a private room to public, switch the guest access to "allow" and switch back the room visibility to private, guest access is hidden but the previous change is kept.

### Steps to reproduce:
1. Activate developer mode in EA advanced settings
2. Go to a private room settings (be sure to have required power level to edit room settings) - guest access is hidden
3. Change the room access to "Public" and save - guest access is visible
4. Allow guests to join
5. Try to go back -> error, there are unsaved changes, okay so cancel
6. Change the room access to "Private" and save (to restore initial state) - guest access is hidden
7. Try to go back -> error, there are still some remaining unsaved changes
8. Change again guest access to forbidden as we did in previous steps
9. Try to go back -> no error, guest access has not changed

https://user-images.githubusercontent.com/11990514/136392175-462da82a-d8ae-4c33-80ca-f899324eafc7.mp4

### Intended result and actual result

#### What did you expect?

Guest access should be changed for public rooms only, probably reset to forbidden for any room with private visibility (or its initial value should be kept when it is hidden)

#### What happened instead?

Guest access is hidden but its value is changed

### Your phone model

_No response_

### Operating system version

_No response_

### Application version and app store

_No response_

### Homeserver

_No response_

### Have you submitted a rageshake?

No