Export billing account map to registrar sheet

The billing account map will be serialized in the following format:

{currency1=id1, currency2=id2, ...}

In order for the output to be deterministic, the billing account map is stored as a sorted map.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=161075814

java/google/registry/export/sheet/SyncRegistrarsSheetAction.java

@@ -81,7 +81,7 @@ public class SyncRegistrarsSheetAction implements Runnable {
     private final int statusCode;
     protected final String message;
 
-    private Result(int statusCode, String message) {
+    Result(int statusCode, String message) {
       this.statusCode = statusCode;
       this.message = message;
     }