Move security consideration to MSC2962
I think the peeking thing is specific to access control.
@@ -282,9 +282,7 @@ One way this might be implemented is:
## Security considerations
-* The peek server has significant power. For example, a poorly chosen peek
- server could lie about the space membership and add an
- `@evil_user:example.org`.
+None at present.
## Tradeoffs
