Fix build by removing Comparable on Project.NameKey

The Comparable interface is inherited through the base class,
StringKey, and does not need to be implemented here anymore.

Change-Id: I6cc8ec8123a2d39782f4be798a9f92548cb129ff

gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/Project.java

@@ -21,7 +21,7 @@ import com.google.gwtorm.client.StringKey;
 public final class Project {
   /** Project name key */
   public static class NameKey extends
-      StringKey<com.google.gwtorm.client.Key<?>> implements Comparable<NameKey> {
+      StringKey<com.google.gwtorm.client.Key<?>>{
     private static final long serialVersionUID = 1L;
 
     @Column(id = 1)
@@ -44,11 +44,6 @@ public final class Project {
       name = newValue;
     }
 
-    @Override
-    public int compareTo(NameKey other) {
-      return get().compareTo(other.get());
-    }
-
     @Override
     public int hashCode() {
       return get().hashCode();