Reduce query batch size for BSA unavailables (#2313)

Query size is borderline too-large for the replica.

At 50000, about 2 out of 30 took more than 30 seconds and were retried.
Lower to 40000 and we will keep monitoring the executions.

core/src/main/java/google/registry/bsa/UploadBsaUnavailableDomainsAction.java

@@ -80,7 +80,7 @@ public class UploadBsaUnavailableDomainsAction implements Runnable {
 
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
-  private static final int BATCH_SIZE = 50000;
+  private static final int BATCH_SIZE = 40000;
 
   Clock clock;