[SPARK-31740][K8S][TESTS] Use github URL instead of a broken link

This PR aims to use GitHub URL instead of a broken link in `BasicTestsSuite.scala`.

Currently, K8s integration test is broken:

https://amplab.cs.berkeley.edu/jenkins/view/Spark%20K8s%20Builds/job/spark-master-test-k8s/534/console

```
- Run SparkRemoteFileTest using a remote data file *** FAILED ***
  The code passed to eventually never returned normally. Attempted 130 times over 2.00109555135 minutes. Last failure message: false was not true. (KubernetesSuite.scala:370)
```

No.

Pass the K8s integration test.

Closes apache#28561 from williamhyun/williamhyun-patch-1.

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

Author: williamhyun

resource-managers/kubernetes/integration-tests/src/test/scala/org/apache/spark/deploy/k8s/integrationtest/BasicTestsSuite.scala

@@ -111,6 +111,6 @@ private[spark] object BasicTestsSuite {
   val CONTAINER_LOCAL_DOWNLOADED_PAGE_RANK_DATA_FILE =
      s"$CONTAINER_LOCAL_FILE_DOWNLOAD_PATH/pagerank_data.txt"
   val REMOTE_PAGE_RANK_DATA_FILE =
-    "https://storage.googleapis.com/spark-k8s-integration-tests/files/pagerank_data.txt"
+    "https://raw.githubusercontent.com/apache/spark/master/data/mllib/pagerank_data.txt"
   val REMOTE_PAGE_RANK_FILE_NAME = "pagerank_data.txt"
 }