fix typo in comments

src/force/nep3_multigpu.cuh

@@ -80,7 +80,7 @@ public:
  bool use_typewise_cutoff = false;
  bool use_typewise_cutoff_zbl = false;
  int num_gpus = 1;
- int version = 2; // NEP version, 2 for NEP2 and 3 for NEP3
+ int version = 4; // NEP version, 3 for NEP3 and 4 for NEP4
  int model_type =
  0; // 0=potential, 1=dipole, 2=polarizability, 3=temperature-dependent free energy
  float rc_radial = 0.0f; // radial cutoff