chore: set new channel pool defaults as package-private

Author: lqiu96

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/DatastoreOptions.java

@@ -56,8 +56,8 @@ public class DatastoreOptions extends ServiceOptions<Datastore, DatastoreOptions
   public static final String PROJECT_ID_ENV_VAR = "DATASTORE_PROJECT_ID";
   public static final String LOCAL_HOST_ENV_VAR = "DATASTORE_EMULATOR_HOST";
   public static final int INIT_CHANNEL_COUNT = 5;
-  public static final int CHANNEL_POOL_DEFAULT_RESIZE_DELTA = 5;
-  public static final int CHANNEL_POOL_MAX_RPCS_PER_CHANNEL = 100;
+  static final int CHANNEL_POOL_DEFAULT_RESIZE_DELTA = 5;
+  static final int CHANNEL_POOL_MAX_RPCS_PER_CHANNEL = 100;
   public static final int MIN_CHANNEL_COUNT = 1;
 
   @ObsoleteApi("This constant is obsolete and will be removed in a future version")