xen: drop stubdomains TODO note

It has been decided in #343111 that we should not build MiniOS
stubdomains, and instead use Linux-based ones for now.

Once MirageOS or Unikraft is packaged, we can switch to using those
microkernels as stubdomains.

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

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

@@ -426,8 +426,6 @@ stdenv.mkDerivation (finalAttrs: {
     "xen" # Build the Xen Hypervisor.
     "tools" # Build the userspace tools, such as `xl`.
     "docs" # Build the Xen Documentation
-    # TODO: Enable the Stubdomains target. This requires another pre-fetched source: mini-os. Currently, Xen appears to build a limited version of stubdomains which does not include mini-os.
-    # "stubdom"
   ];
 
   enableParallelBuilding = true;