nixos/fail2ban: Update openssh option in docs

The
```
services.openssh.logLevel
```
option has been changed to
```
services.openssh.settings.LogLevel
```
since cf10d7aef8ff9ca0e178e87981d9e4fd3018193c and this service is
already using the new option (on line 462) but the description just
hasn't been updated.

The `option` formatting as also been updated by the suggestion of
@Defelo

Changed files
+2 -2
nixos
modules
services
security
+2 -2
nixos/modules/services/security/fail2ban.nix
···
description = ''
Whether to enable the fail2ban service.
-
See the documentation of {option}`services.fail2ban.jails`
+
See the documentation of [](#opt-services.fail2ban.jails)
for what jails are enabled by default.
'';
};
···
NixOS comes with a default `sshd` jail;
for it to work well,
-
{option}`services.openssh.logLevel` should be set to
+
[](#opt-services.openssh.settings.LogLevel) should be set to
`"VERBOSE"` or higher so that fail2ban
can observe failed login attempts.
This module sets it to `"VERBOSE"` if