Remove duplicate save attribute.

There is already a blanket save statement for the entire module, so these save attributes induce a warning on newer compilers.

For example, with gfortran,
```
axisem/SOLVER/nc_routines.F90:1570.24:
    use data_mesh, only: npoint_plot
                        1
Error: Symbol 'npoint_plot' referenced at (1) not found in module 'data_mesh'
```