Maint: OpenVPN option: remove all ping-* options

- Use the built-in healthcheck vpn restart mechanism instead
- Restarting with `ping-restart` or `ping-exit` would only restart with the same `remote` connection
- Specify `ping` options as VPN specific to ensure the server doesn't disconnect us

internal/provider/nordvpn/openvpnconf.go

@@ -36,7 +36,6 @@ func (n *Nordvpn) BuildConf(connection models.Connection,
 		"reneg-sec 0",
 		"key-direction 1",
 		"ping 15",
-		"ping-restart 0",
 
 		// Added constant values
 		"auth-nocache",