fix: correct inheritance typo in sizeof example

Fix typo where C1 should inherit from A1 instead of A

basic_content/sizeof/geninhe.cpp

@@ -49,7 +49,7 @@ class C {
 class A1 {
   virtual void fun() {}
 };
-class C1 : public A {};
+class C1 : public A1 {};
 
 int main() {
   cout << sizeof(A) << endl; // 8