Libraries: Use default constructors/destructors in LibJS

https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#cother-other-default-operation-rules

"The compiler is more likely to get the default semantics right and
you cannot implement these functions better than the compiler."

Userland/Libraries/LibJS/Runtime/Map.h

@@ -23,7 +23,7 @@ public:
     static Map* create(GlobalObject&);
 
     explicit Map(Object& prototype);
-    virtual ~Map() override;
+    virtual ~Map() override = default;
 
     void map_clear();
     bool map_remove(Value const&);