C.61: Fixed example to use `new[]` instead to allocate an array.

CppCoreGuidelines.md

@@ -4603,7 +4603,7 @@ After a copy `x` and `y` can be independent objects (value semantics, the way no
     }
 
     X::X(const X& a)
-        :p{new T}, sz{a.sz}
+        :p{new T[a.sz]}, sz{a.sz}
     {
         copy(a.p, a.p + sz, a.p);
     }