Remove unenforced size limit on room names (#3669)

Fixes #3641

The spec says the name field in m.room.name events must not exceed 255 bytes but no servers actually enforce this over the C-S API. Clients should probably already be truncating room names to an appropriate length for their user interface.

Signed-off-by: Aaron Raimist <aaron@raim.ist>

changelogs/client_server/newsfragments/3669.clarification

@@ -0,0 +1 @@
+Remove unenforced size limit on the `name` field of `m.room.name` events.

data/event-schemas/schema/m.room.name.yaml

@@ -17,7 +17,7 @@ properties:
   content:
     properties:
       name:
-        description: The name of the room. This MUST NOT exceed 255 bytes.
+        description: The name of the room.
         type: string
     required:
       - name