LibWeb: Add calls to JS_{DECLARE,DEFINE}_ALLOCATOR()

Author: https://github.com/mattco98
Commit: 31341b280a
Pull-request: https://github.com/SerenityOS/serenity/pull/23878
Issue: https://github.com/SerenityOS/serenity/issues/23805
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/Streams/ReadableStreamDefaultReader.h

@@ -33,6 +33,7 @@ public:
 
 class ReadLoopReadRequest final : public ReadRequest {
     JS_CELL(ReadLoopReadRequest, JS::Cell);
+    JS_DECLARE_ALLOCATOR(ReadLoopReadRequest);
 
 public:
     // successSteps, which is an algorithm accepting a byte sequence