LibJS: Call the correct base class in LexicalEnvironment::visit_edges()

We were calling directly up to Cell, skipping over ScopeObject.
This made us not mark the scope chain parent for lexical environments,
sometimes causing them to get GC'd and use-after-free'd.

Found by Fuzzilli.

Fixes #5140.

Userland/Libraries/LibJS/Runtime/LexicalEnvironment.cpp

@@ -63,7 +63,7 @@ LexicalEnvironment::~LexicalEnvironment()
 
 void LexicalEnvironment::visit_edges(Visitor& visitor)
 {
-    Cell::visit_edges(visitor);
+    Base::visit_edges(visitor);
     visitor.visit(m_this_value);
     visitor.visit(m_home_object);
     visitor.visit(m_new_target);