[SPARK-54794][CORE] Suppress verbose FsHistoryProvider.checkForLogs scanning logs

### What changes were proposed in this pull request?

This PR aims to suppress verbose `FsHistoryProvider.checkForLogs` scanning logs.

### Why are the changes needed?

This is a kind of regression at Apache Spark 4.1.0 switched from `logDebug` to `logInfo` accidentally. We had better recover them back to `DEBUG` level because it's excessively verbose currently.
- #52382

```
25/12/21 22:27:53 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356063285
25/12/21 22:28:03 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356073312
25/12/21 22:28:13 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356083338
25/12/21 22:28:23 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356093347
25/12/21 22:28:33 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356103369
25/12/21 22:28:43 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356113391
25/12/21 22:28:53 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356123402
25/12/21 22:29:03 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356133422
25/12/21 22:29:13 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356143443
25/12/21 22:29:23 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356153458
25/12/21 22:29:33 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356163471
25/12/21 22:29:43 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356173491
25/12/21 22:29:53 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356183502
25/12/21 22:30:03 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356193517
25/12/21 22:30:13 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356203529
25/12/21 22:30:23 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356213555
25/12/21 22:30:33 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356223567
25/12/21 22:30:43 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356233585
25/12/21 22:30:53 INFO FsHistoryProvider: Scanning s3a://spark-events with lastScanTime=1766356243599
```

### Does this PR introduce _any_ user-facing change?

No behavior change except log message level.

### How was this patch tested?

Pass the CIs.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes #53555 from dongjoon-hyun/SPARK-54794.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Kousuke Saruta <[email protected]>

Author: dongjoon-hyun

core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala

@@ -502,7 +502,7 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
     var count: Int = 0
     try {
       val newLastScanTime = clock.getTimeMillis()
-      logInfo(log"Scanning ${MDC(HISTORY_DIR, logDir)} with " +
+      logDebug(log"Scanning ${MDC(HISTORY_DIR, logDir)} with " +
         log"lastScanTime=${MDC(LAST_SCAN_TIME, lastScanTime)}")
 
       // Mark entries that are processing as not stale. Such entries do not have a chance to be