Fix generics in EppXmlTransformer.unmarshal to not be only on the return type.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=124914271

java/google/registry/flows/domain/DomainFlowUtils.java

@@ -497,7 +497,7 @@ public class DomainFlowUtils {
 
     SignedMark signedMark;
     try {
-      signedMark = unmarshal(signedMarkData);
+      signedMark = unmarshal(SignedMark.class, signedMarkData);
     } catch (EppException e) {
       throw new SignedMarkParsingErrorException();
     }