Remove @VisibleForTesting annotation on ChangeKindCacheImpl#NoCache

It is not used in any tests.  It is useful when using Gerrit as a
library, so let's make this helper an ordinary public class.

Noticed via an error-prone warning about a Google-internal caller.

Change-Id: I6fe9f8a792b7fa9328f95aa97893bcec78db367a

java/com/google/gerrit/server/change/ChangeKindCacheImpl.java

@@ -79,7 +79,6 @@ public class ChangeKindCacheImpl implements ChangeKindCache {
     };
   }
 
-  @VisibleForTesting
   public static class NoCache implements ChangeKindCache {
     private final boolean useRecursiveMerge;
     private final ChangeData.Factory changeDataFactory;