Rename async flow failure backoff config property

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=118207124

java/com/google/domain/registry/config/TestRegistryConfig.java

@@ -190,7 +190,7 @@ public class TestRegistryConfig implements RegistryConfig {
   }
 
   @Override
-  public Duration getAsyncDeleteFlowFailureBackoff() {
+  public Duration getAsyncFlowFailureBackoff() {
     return Duration.standardMinutes(10);
   }
 }