nixosTests.gitlab: do not block nixos-unstable on aarch64

gitlab (or its test) commonly needs work to keep succeeding,
and currently I fail to see energy to keep it in sufficient shape
for aarch64 to remain a channel blocker.  (x86_64 still will be)

Author: vcunat

nixos/release-combined.nix

@@ -99,7 +99,7 @@ rec {
 
         (onFullSupported "nixos.tests.firewall")
         (onFullSupported "nixos.tests.fontconfig-default-fonts")
-        (onFullSupported "nixos.tests.gitlab")
+        (onSystems [ "x86_64-linux" ] "nixos.tests.gitlab") # we lack energy to really debug aarch64 here
         (onFullSupported "nixos.tests.gnome")
         (onFullSupported "nixos.tests.gnome-xorg")
         (onSystems [ "x86_64-linux" ] "nixos.tests.hibernate")