nixos/release-small: stop building amazon image

Rebuilding images multiple times on the small channels is too expensive
and makes them slower than they could be. Consuming the image from the
full release channel is probably good enough.

nixos/release-small.nix

@@ -32,7 +32,7 @@ let
 in rec {
 
   nixos = {
-    inherit (nixos') channel manual options iso_minimal amazonImage dummy;
+    inherit (nixos') channel manual options iso_minimal dummy;
     tests = {
       inherit (nixos'.tests)
         acme
@@ -116,7 +116,6 @@ in rec {
       (map onSupported [
         "nixos.dummy"
         "nixos.iso_minimal"
-        "nixos.amazonImage"
         "nixos.manual"
         "nixos.tests.acme"
         "nixos.tests.boot.uefiCdrom"