release-combined: don't include tests.chromium

The chromium package will frequently time out . Note that this is unrelated to the test but a side effect because the test depends on chromium.

https://hydra.nixos.org/job/nixos/trunk-combined/nixos.tests.chromium.x86_64-linux

See also #39476

nixos/release-combined.nix

@@ -58,7 +58,7 @@ in rec {
         nixos.ova.x86_64-linux or []
 
         #(all nixos.tests.containers)
-        nixos.tests.chromium.x86_64-linux or []
+        #nixos.tests.chromium.x86_64-linux or []
         (all nixos.tests.firefox)
         (all nixos.tests.firewall)
         (all nixos.tests.gnome3)