Clean up some code quality issues

This removes some qualifiers that aren't necessary (e.g. public/abstract on interfaces, private on enum constructors, final on private methods, static on nested interfaces/enums), uses Java 8 lambdas and features where that's an improvement

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=177182945

java/google/registry/reporting/IcannHttpReporter.java

@@ -121,8 +121,7 @@ public class IcannHttpReporter {
     XjcIirdeaResponseElement response =
         XjcXmlTransformer.unmarshal(
             XjcIirdeaResponseElement.class, new ByteArrayInputStream(content));
-    XjcIirdeaResult result = response.getResult();
-    return result;
+    return response.getResult();
   }
 
   /** Verifies a given report filename matches the pattern tld-reportType-yyyyMM.csv. */