Delete unused description field from premium/reserved list entities

It isn't used now, and as far as I can tell it was never used for anything, so
get rid of it.  We won't be using it in our new Cloud SQL schema anyway.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=242501877

javatests/google/registry/tools/server/ListPremiumListsActionTest.java

@@ -52,11 +52,11 @@ public class ListPremiumListsActionTest extends ListActionTestCase {
   public void testRun_withParameters() {
     testRunSuccess(
         action,
-        Optional.of("revisionKey,description"),
+        Optional.of("revisionKey"),
         Optional.empty(),
         Optional.empty(),
-        "^name\\s+revisionKey\\s+description\\s*$",
-        "^-+\\s+-+\\s+-+\\s*$",
+        "^name\\s+revisionKey\\s*$",
+        "^-+\\s+-+\\s*$",
         "^how\\s+.*PremiumList.*$",
         "^xn--q9jyb4c\\s+.*PremiumList.*$");
   }