Fix Iterable generation caused by iterable dts merging (microsoft#2399)

Co-authored-by: saschanaz <saschanaz@users.noreply.github.com>

Author: jakebailey

baselines/audioworklet.generated.d.ts

@@ -2046,7 +2046,7 @@ type ReadableStreamType = "bytes";
 
 interface MessageEvent<T = any> {
     /** @deprecated */
-    initMessageEvent(type: string, bubbles?: boolean, cancelable?: boolean, data?: any, origin?: string, lastEventId?: string, source?: MessageEventSource | null, ports?: MessagePort[]): void;
+    initMessageEvent(type: string, bubbles?: boolean, cancelable?: boolean, data?: any, origin?: string, lastEventId?: string, source?: MessageEventSource | null, ports?: Iterable<MessagePort>): void;
 }
 
 interface URLSearchParamsIterator<T> extends IteratorObject<T, BuiltinIteratorReturn, unknown> {