nixos/systemd-stage-1: Order nixos activation after initrd-switch-root.target

Now it's placed between initrd-switch-root.target and
initrd-switch-root.service, meaning it is truly the last thing to
happen before switch-root, as it should be.

Author: ElvishJerricco

nixos/modules/system/boot/systemd/initrd.nix

@@ -581,14 +581,10 @@ in {
       ];
 
       services.initrd-nixos-activation = {
-        requires = [
-          config.boot.initrd.systemd.services.initrd-find-nixos-closure.name
-        ];
-        after = [
-          "initrd-fs.target"
-          config.boot.initrd.systemd.services.initrd-find-nixos-closure.name
-        ];
-        requiredBy = [ "initrd.target" ];
+        after = [ "initrd-switch-root.target" ];
+        requiredBy = [ "initrd-switch-root.service" ];
+        before = [ "initrd-switch-root.service" ];
+        unitConfig.DefaultDependencies = false;
         unitConfig = {
           AssertPathExists = "/etc/initrd-release";
           RequiresMountsFor = [