Add escrow file import validation logic

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=129116064

java/google/registry/config/RegistryConfig.java

@@ -89,11 +89,6 @@ public interface RegistryConfig {
    */
   public String getZoneFilesBucket();
 
-  /**
-   * Returns the Google Cloud Storage bucket for importing escrow files.
-   */
-  public String getEscrowFileImportBucket();
-
   /**
    * Returns {@code true} if TMCH certificate authority should be in testing mode.
    *