[CELEBORN-2279] Update log level from INFO to ERROR for console output in spark-it tests

### What changes were proposed in this pull request?
Update log level from `INFO` to `ERROR` for console output in spark-it tests.

### Why are the changes needed?
`spark-it` outputs too many INFO level logs to stdout.

<img width="1017" height="143" alt="image" src="https://github.com/user-attachments/assets/41667a37-050b-4174-afe6-6e4afcda8fcc" />

<img width="783" height="188" alt="image" src="https://github.com/user-attachments/assets/6bb4f3e3-223d-4f8c-bea6-4c8d451bf4b9" />

### Does this PR resolve a correctness bug?
No

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
GHA

Closes #3623 from cxzl25/CELEBORN-2279.

Authored-by: sychen <sychen@ctrip.com>
Signed-off-by: 子懿 <ziyi.jxf@antgroup.com>

Author: cxzl25

tests/spark-it/src/test/resources/log4j2-test.xml

@@ -21,7 +21,7 @@
         <Console name="stdout" target="SYSTEM_OUT">
             <PatternLayout pattern="%d{yy/MM/dd HH:mm:ss,SSS} %p [%t] %c{1}: %m%n%ex"/>
             <Filters>
-                <ThresholdFilter level="INFO"/>
+                <ThresholdFilter level="ERROR"/>
             </Filters>
         </Console>
         <File name="file" fileName="target/unit-tests.log">