Update index.d.ts (#1037)

docs/index.d.ts

@@ -229,7 +229,7 @@ export interface WebSocketBehavior<UserData> {
     /** Maximum length of received message. If a client tries to send you a message larger than this, the connection is immediately closed. Defaults to 16 * 1024. */
     maxPayloadLength?: number;
     /** Whether or not we should automatically close the socket when a message is dropped due to backpressure. Defaults to false. */
-    closeOnBackpressureLimit?: number;
+    closeOnBackpressureLimit?: boolean;
     /** Maximum number of minutes a WebSocket may be connected before being closed by the server. 0 disables the feature. */
     maxLifetime?: number;
     /** Maximum amount of seconds that may pass without sending or getting a message. Connection is closed if this timeout passes. Resolution (granularity) for timeouts are typically 4 seconds, rounded to closest.