Replace mjs_deleteBody with mjs_delete.

PiperOrigin-RevId: 639058333
Change-Id: I9ac9ca8c6b8c0219f0130cd65dc83602f1829684

src/user/user_objects.h

@@ -208,10 +208,11 @@ class mjCBase : public mjCBase_ {
   mjCFrame* frame;                // pointer to frame transformation
   mjCModel* model;                // pointer to model that created object
 
+  virtual ~mjCBase() = default;   // destructor
+
  protected:
   mjCBase();                                 // constructor
   mjCBase(const mjCBase& other);             // copy constructor
-  virtual ~mjCBase() = default;              // destructor
 };