nixos/evremap: get rid of unecessary bash

Using `systemd.services.<name>.script` pulls in bash in the ExecStart
line for a service. Since our "script" was only one line anyways,
we can inline it to just use ExecStart directly. Losing shell features
shouldn't be detrimental here, as we're not using pipes and there are
no globs to expand.

nixos/modules/services/misc/evremap.nix

@@ -131,9 +131,9 @@ in
       description = "evremap - keyboard input remapper";
       wantedBy = [ "multi-user.target" ];
 
-      script = "${lib.getExe pkgs.evremap} remap ${configFile}";
-
       serviceConfig = {
+        ExecStart = "${lib.getExe pkgs.evremap} remap ${configFile}";
+
         DynamicUser = true;
         User = "evremap";
         SupplementaryGroups = [