LibJS: Fix that proxy always said that it had a [[Construct]] slot

Author: https://github.com/davidot
Commit: 021691753d
Pull-request: https://github.com/SerenityOS/serenity/pull/10483
Issue: https://github.com/SerenityOS/serenity/issues/8198
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Runtime/ProxyObject.h

@@ -22,7 +22,7 @@ public:
     virtual ~ProxyObject() override;
 
     virtual const FlyString& name() const override;
-    virtual bool has_constructor() const override { return true; }
+    virtual bool has_constructor() const override;
 
     const Object& target() const { return m_target; }
     const Object& handler() const { return m_handler; }