Remove cycle breaking algorithm to be specced in the future, if necessary.

proposals/1772-groups-as-rooms.md

@@ -187,19 +187,6 @@ Cycles in the parent->child and child->parent relationships are *not*
 permitted, but clients (and servers) should be aware that they may be
 encountered, and MUST spot and break cycles rather than infinitely looping.
 
-In order for UI to be consistent across different clients, any cycles must be
-cut deterministically.  For instance, if space A points to space B as a child
-but space B also points to space A as a child, then clients must be consistent
-on whether A is shown in the UI as the parent of B (or vice versa).  Therefore
-when a client needs to consistently visualise a space hierarchy, it should
-check for loops in parent->child or child->parent relationships and ignore the
-cycle by cutting it such that the oldest space-room is the root (i.e. oldest
-parent). 'Oldest' means the room whose `m.room.create` event has the
-numerically smallest `origin_server_ts`.  If the oldest rooms are precisely
-the same age, we select the root as the room with the smallest `room_id`
-(lexicographically comparing the Unicode code-points of the `room_id` string).
-https://hackmd.io/eQpyqCcRR-Gj-SWZcD-Fxg shows an algorithm for doing so.
-
 ### Suggested children
 
 Space admins can mark particular children of a space as "suggested". This