chore(3p/nixpkgs): bump channels (2025-04-21)

* Update Snix' verify-lang-tests to 2.28, as 2.25 has been removed
   from nixpkgs
 * Update snix/cli integration tests, iso_gnome is called iso_graphical
   (again?)
 * Address clippy lints
 * Regenerate go bindings
 * Remove grpc-health-check from our overlay, it's long been merged

Change-Id: I9d33cabdd3e7065a1f28bcccf4f979f08a456f88
Reviewed-on: https://cl.snix.dev/c/snix/+/30333
Reviewed-by: Ilan Joselevich <personal@ilanjoselevich.com>
Autosubmit: Florian Klink <flokli@flokli.de>
Tested-by: besadii

third_party/sources/sources.json

@@ -97,10 +97,10 @@
         "homepage": "",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "c80f6a7e10b39afcc1894e02ef785b1ad0b0d7e5",
-        "sha256": "1sfb9g6fmyfligcsd1rmkamfqvy8kgn3p0sy8ickf6swi1zdbf0b",
+        "rev": "c11863f1e964833214b767f4a369c6e6a7aba141",
+        "sha256": "17d9zxpqxp54gz4zv4j4g0wb8c4i29j4q76xah8zi4bh7hrp5yhr",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/c80f6a7e10b39afcc1894e02ef785b1ad0b0d7e5.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/c11863f1e964833214b767f4a369c6e6a7aba141.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs-stable": {