Don't make chromium-beta/dev release blockers

Generally we shouldn't ship pre-release versions anyway, and we
certainly don't want them to be release blockers. Also, chromium
builds are just too slow to have them blocking the channel (see
https://github.com/NixOS/nixpkgs/issues/12794).

Changed files
+2 -2
nixos
tests
+2 -2
nixos/tests/chromium.nix
···
{ pkgs
, channelMap ? {
stable = pkgs.chromium;
-
beta = pkgs.chromiumBeta;
-
dev = pkgs.chromiumDev;
+
#beta = pkgs.chromiumBeta;
+
#dev = pkgs.chromiumDev;
}
, ...
}: rec {