update relation string to match msc

Author: toger5

src/@types/event.ts

@@ -163,8 +163,8 @@ export enum RelationType {
     // moreover, our tests currently use the unstable prefix. Use THREAD_RELATION_TYPE.name.
     // Once we support *only* the stable prefix, THREAD_RELATION_TYPE can die and we can switch to this.
     Thread = "m.thread",
-    unstable_RTCParentEvent = "org.matrix.msc4075.rtc.parent_event",
-    unstable_RTCDecline = "org.matrix.msc4075.rtc.decline",
+    unstable_RTCNotificationParent = "org.matrix.msc4075.rtc.notification.parent",
+    unstable_RTCNotificationDecline = "org.matrix.msc4075.rtc.notification.decline",
 }
 
 export enum MsgType {

src/matrixrtc/MatrixRTCSession.ts

@@ -582,7 +582,7 @@ export class MatrixRTCSession extends TypedEventEmitter<
                     "notification_type": notificationType,
                     "m.relates_to": {
                         event_id: parentEventId,
-                        rel_type: RelationType.unstable_RTCParentEvent,
+                        rel_type: RelationType.unstable_RTCNotificationParent,
                     },
                     "sender_ts": Date.now(),
                     "lifetime": 30_000, // 30 seconds