Remove unnecessary type specifications

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=179585680

javatests/google/registry/export/CheckSnapshotActionTest.java

@@ -86,7 +86,7 @@ public class CheckSnapshotActionTest {
         new DatastoreBackupInfo(
             backupInfo.getName(),
             backupInfo.getStartTime(),
-            Optional.<DateTime>empty(),
+            Optional.empty(),
             backupInfo.getKinds(),
             backupInfo.getGcsFilename());