Use relativePath for K8s remote file test in BasicTestsSuite

$ build/sbt -Pkubernetes -Pkubernetes-integration-tests -Dspark.kubernetes.test.dockerFile=resource-managers/kubernetes/docker/src/main/dockerfiles/spark/Dockerfile.java17 -Dtest.exclude.tags=minikube,r "kubernetes-integration-tests/test"
...
[info] KubernetesSuite:
...
[info] - Run SparkRemoteFileTest using a remote data file *** FAILED *** (3 minutes, 3 seconds)
[info]   The code passed to eventually never returned normally. Attempted 190 times over 3.012265011116667 minutes. Last failure message: false was not true. (KubernetesSuite.scala:452)
... 

$ build/sbt -Pkubernetes -Pkubernetes-integration-tests -Dspark.kubernetes.test.dockerFile=resource-managers/kubernetes/docker/src/main/dockerfiles/spark/Dockerfile.java17 -Dtest.exclude.tags=minikube,r "kubernetes-integration-tests/test"
...
[info] KubernetesSuite:
...
[info] - Run SparkRemoteFileTest using a remote data file (8 seconds, 608 milliseconds)