nixos/openvpn: tidy systemd restart-after-sleep unit

On reviewing my PR #345993, I spotted I'd failed to remove a
now-unneeded package and failed to update the systemd unit description,
so tidy that up.

nixos/modules/services/networking/openvpn.nix

@@ -85,13 +85,12 @@ let
   restartService = optionalAttrs cfg.restartAfterSleep {
     openvpn-restart = {
       wantedBy = [ "sleep.target" ];
-      path = [ pkgs.procps ];
       script =
         let
           unitNames = map (n: "openvpn-${n}.service") (builtins.attrNames cfg.servers);
         in
         "systemctl try-restart ${lib.escapeShellArgs unitNames}";
-      description = "Sends a signal to OpenVPN process to trigger a restart after return from sleep";
+      description = "Restart system OpenVPN connections when returning from sleep";
     };
   };