Auto merge of #29465 - 2shiori17:issue-29388, r=jdm

Implement Headers.prototype.getSetCookie

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- [x] These changes fix #29388

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components/script/dom/webidls/Headers.webidl

@@ -15,6 +15,7 @@ interface Headers {
   undefined delete(ByteString name);
   [Throws]
   ByteString? get(ByteString name);
+  sequence<ByteString> getSetCookie();
   [Throws]
   boolean has(ByteString name);
   [Throws]