Remove more unnecessary "throws" declarations

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=201243722

javatests/google/registry/export/DatastoreBackupServiceTest.java

@@ -78,7 +78,7 @@ public class DatastoreBackupServiceTest {
   }
 
   @Test
-  public void testSuccess_launchBackup() throws Exception {
+  public void testSuccess_launchBackup() {
     backupService.launchNewBackup(
         "export-snapshot", "backup1", "somebucket", ImmutableSet.of("foo", "bar"));
     assertTasksEnqueued("export-snapshot",