hetzner-nixops-install: Correct typo in meta attr.

I think it's called maintainerS :-)

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

pkgs/tools/misc/hetzner-nixops-installer/default.nix

@@ -102,6 +102,6 @@ in stdenv.mkDerivation {
                        (remember, we're on a non-NixOS system here), together
                        with the partitioner.
     '';
-    maintainer = stdenv.lib.maintainers.aszlig;
+    maintainers = [ stdenv.lib.maintainers.aszlig ];
   };
 }