Remove reference to 'this MSC'.

data/event-schemas/schema/m.call.negotiate.yaml

@@ -27,12 +27,12 @@ description: |
   another `m.call.negotiate` event, with the SDP answer (with `"type": "answer"`)
   in the `description` property.
 
-  This MSC also proposes clarifying the `m.call.invite` and `m.call.answer`
-  events to state that the `offer` and `answer` fields respectively are objects
-  of type `RTCSessionDescriptionInit`.  Hence the `type` field, whilst
-  redundant in these events, is included for ease of working with the WebRTC
-  API and is mandatory. Receiving clients should not attempt to validate the
-  `type` field, but simply pass the object into the WebRTC API.
+  In the `m.call.invite` and `m.call.answer` events, the `offer` and `answer`
+  fields respectively are objects of type `RTCSessionDescriptionInit`.  Hence
+  the `type` field, whilst redundant in these events, is included for ease of
+  working with the WebRTC API and is mandatory. Receiving clients should not
+  attempt to validate the `type` field, but simply pass the object into the
+  WebRTC API.
 allOf:
 - "$ref": core-event-schema/room_event.yaml
 properties: