WCOSS2 gempak ush scripts updates and cleanup of old release notes (#920

)

* WCOSS2 updates to gempak ush scripts

- Add /gempak subfolder where needed in gempak ush scripts.
- Remove unneeded commented out path settings from older iterations.

* Removing older release notes

- Cleaning out older GFS version release notes; includes current GFSv16.2.1 release notes, will commit GFSv16.3
release notes with implementation this fall.
- Will then keep only the latest release notes moving forward.

Refs: #419