Don't refer to MSC3779 explicitly in comment (#2533)

because other MSCs (like 3757) may allow @-prefixed state keys

src/widget.ts

@@ -138,7 +138,7 @@ export const widget = ((): WidgetHelpers | null => {
       const sendState = [
         userId, // Legacy call membership events
         `_${userId}_${deviceId}`, // Session membership events
-        `${userId}_${deviceId}`, // MSC3779 session membership events
+        `${userId}_${deviceId}`, // The above with no leading underscore, for room versions whose auth rules allow it
       ].map((stateKey) => ({
         eventType: EventType.GroupCallMemberPrefix,
         stateKey,