Debug indexingRescanOnOverflow test

Author: sungshik

src/test/java/engineering/swat/watch/SingleDirectoryTests.java

@@ -230,6 +230,7 @@ public void execute(Runnable command) {
             });
 
         try (var watch = watchConfig.start()) {
+            Thread.sleep(TestHelper.NORMAL_WAIT.toMillis());
             // At this point, the index of last-modified-times inside `watch` is
             // populated with initial values.