man: drop version info from file hiearchy man page

man: drop version info from file hiearchy man page

This file doesn't document features of systemd, but is more a of a
general description that generalizes/modernizes FHS. As such, the items
listed in it weren't "added" in systemd versions, they simply reflect
general concepts independent of any specific systemd version. hence
let's drop this misleading and confusing version info.

Or in other words, the man page currently claims under "/usr/": "Added
in version 215." – Which of course is rubbish, the directory existed
since time began.

This also rebreaks all paragaphs this touches.

No content changes.

(cherry picked from commit 26db8fe2478316825c5596e4b93b08176a8abddb)