xen: make meta.maintainers more friendly for new contributors

From Peder Sundt:
> I read maintainers = with lib.maintainers; [ ]; as a friendly open
> invitation, while maintainers = [ ]; as a sad state of reality.
> I want people to join the project hence I very much prefer the former.

I don't plan on leaving anytime soon, but let's not make it
more difficult for new maintainers to step up.

Signed-off-by: Fernando Rodrigues <alpha@sigmasquadron.net>

pkgs/applications/virtualization/xen/generic/default.nix

@@ -664,7 +664,7 @@ stdenv.mkDerivation (finalAttrs: {
       # Development headers in $dev/include.
       mit
     ];
-    maintainers = [ lib.maintainers.sigmasquadron ];
+    maintainers = with lib.maintainers; [ sigmasquadron ];
     mainProgram = "xl";
     # Evaluates to x86_64-linux.
     platforms = lib.lists.intersectLists lib.platforms.linux lib.platforms.x86_64;