### What changes were proposed in this pull request?
Upgrade Kubernetes Client Version to 5.6.0.
### Why are the changes needed?
The exponential backoff feature is extended with one more case:
[ Retry HTTP operation in case IOException too (exponential backoff)](https://github.com/fabric8io/kubernetes-client/pull/3293)
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Tested with existing unit and integration tests:
```
KubernetesSuite:
- Run SparkPi with no resources
- Run SparkPi with a very long application name.
- Use SparkLauncher.NO_RESOURCE
- Run SparkPi with a master URL without a scheme.
- Run SparkPi with an argument.
- Run SparkPi with custom labels, annotations, and environment variables.
- All pods have the same service account by default
- Run extraJVMOptions check on driver
- Run SparkRemoteFileTest using a remote data file
- Verify logging configuration is picked from the provided SPARK_CONF_DIR/log4j.properties
- Run SparkPi with env and mount secrets.
- Run PySpark on simple pi.py example
- Run PySpark to test a pyfiles example
- Run PySpark with memory customization
- Run in client mode.
- Start pod creation from template
- Launcher client dependencies
- SPARK-33615: Launcher client archives
- SPARK-33748: Launcher python client respecting PYSPARK_PYTHON
- SPARK-33748: Launcher python client respecting spark.pyspark.python and spark.pyspark.driver.python
- Launcher python client dependencies using a zip file
- Test basic decommissioning
- Test basic decommissioning with shuffle cleanup
- Test decommissioning with dynamic allocation & shuffle cleanups
- Test decommissioning timeouts
...
[INFO] BUILD SUCCESS
```
Closes#33593 from attilapiros/SPARK-36358.
Authored-by: attilapiros <piros.attila.zsolt@gmail.com>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>
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