systemd: remove redundant lines from system unit — heartwood

A section of this file got duplicated the last time it was edited. This patch removes that superfluos part.

 # `rad auth`.
 #Environment=RAD_PASSPHRASE=snickerdoodle
 # Basic hardening options. For more, please refer to `systemd-analyze security`.
 PrivateTmp=true
 ProtectSystem=strict
 NoNewPrivileges=true
 MemoryDenyWriteExecute=true
 User=seed
 Group=seed