Revert "Make GerritApiImpl class public"

This reverts commit 727d718b77.

Reason for revert: We actually don't need this class to be public.

Change-Id: I25ceacb6e29f8e655bc5a28343d15b2e65aa3981

java/com/google/gerrit/server/api/GerritApiImpl.java

@@ -25,7 +25,7 @@ import com.google.inject.Inject;
 import com.google.inject.Singleton;
 
 @Singleton
-public class GerritApiImpl implements GerritApi {
+class GerritApiImpl implements GerritApi {
   private final Accounts accounts;
   private final Changes changes;
   private final Config config;