Update inaccurate USM Fortran example

[bkmgit]

Summary

The USM example for Fortran references cpp files and does not correspond to the C++ example
in using USM in more than one location

URLs

https://github.com/oneapi-src/oneAPI-samples/blob/master/DirectProgramming/Fortran/Jupyter/OpenMP-offload-training/USM/Unified_Shared_Memory.ipynb

Additional details

Remove references to .cpp files and update data movement examples