[hotfix][test] Adds back timestamp to log output

This was accidentally removed with the changes of FLINK-34417

Author: XComp

flink-tests/src/test/resources/log4j2-test.properties

@@ -28,7 +28,7 @@ appender.testlogger.name = TestLogger
 appender.testlogger.type = CONSOLE
 appender.testlogger.target = SYSTEM_ERR
 appender.testlogger.layout.type = PatternLayout
-appender.testlogger.layout.pattern = [%-32X{flink-job-id}] %c{0} [%t] %-5p %m%n
+appender.testlogger.layout.pattern =  %-4r [%-32X{flink-job-id}] %c{0} [%t] %-5p %m%n
 
 logger.migration.name = org.apache.flink.test.migration
 logger.migration.level = INFO