T905: Delete old op-mode command show remote-config

The op-mode command `show remote-config` did not work for several
years. Since it uses the old backend we should delete it now.
Will be redefined if necessary with a separate task, PR

```
vyos@r1:~$ show remote-config

  Invalid command: show remote-config [invalid]

vyos@r1:~$ show remote-config

  Incomplete command: show remote-config

vyos@r1:~$

```