[SPARK-28357][CORE][TEST] Fix Flaky Test - FileAppenderSuite.rollingfile appender - size-based rolling compressed

## What changes were proposed in this pull request?

`SizeBasedRollingPolicy.shouldRollover` returns false when the size is equal to `rolloverSizeBytes`.
```scala
  /** Should rollover if the next set of bytes is going to exceed the size limit */
  def shouldRollover(bytesToBeWritten: Long): Boolean = {
    logDebug(s"$bytesToBeWritten + $bytesWrittenSinceRollover > $rolloverSizeBytes")
    bytesToBeWritten + bytesWrittenSinceRollover > rolloverSizeBytes
  }
```
- https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/107553/testReport/org.apache.spark.util/FileAppenderSuite/rolling_file_appender___size_based_rolling__compressed_/
```
org.scalatest.exceptions.TestFailedException: 1000 was not less than 1000
```

## How was this patch tested?

Pass the Jenkins with the updated test.

Closes #25125 from dongjoon-hyun/SPARK-28357.

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

Author: dongjoon-hyun

core/src/test/scala/org/apache/spark/util/FileAppenderSuite.scala

@@ -128,7 +128,7 @@ class FileAppenderSuite extends SparkFunSuite with BeforeAndAfter with Logging {
     val files = testRolling(appender, testOutputStream, textToAppend, 0, isCompressed = true)
     files.foreach { file =>
       logInfo(file.toString + ": " + file.length + " bytes")
-      assert(file.length < rolloverSize)
+      assert(file.length <= rolloverSize)
     }
   }