fancontrol: fix path by using lib.getExe' (NixOS#375835)

Author: r-vdp

nixos/modules/services/hardware/fancontrol.nix

@@ -41,7 +41,7 @@ in
 
       serviceConfig = {
         Restart = "on-failure";
-        ExecStart = "${pkgs.lm_sensors}/sbin/fancontrol ${configFile}";
+        ExecStart = "${lib.getExe' pkgs.lm_sensors "fancontrol"} ${configFile}";
       };
     };