[SPARK-52774] Fix resourceRetentionPolicy typo to resourceRetainPolicy in docs

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

This fixes typo in docs regarding resourceRetainPolicy

### Why are the changes needed?

For docs sanity

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

No

### How was this patch tested?

pass CIs

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

No

Closes #284 from jiangzho/typofix.

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

Author: jiangzho

docs/spark_custom_resources.md

@@ -289,11 +289,11 @@ On the other hand, when developing an application, it's possible to configure
 ```yaml
 applicationTolerations:
   # Acceptable values are 'Always', 'OnFailure', 'Never'
-  resourceRetentionPolicy: OnFailure
+  resourceRetainPolicy: OnFailure
 ```
 
 to avoid operator attempt to delete driver pod and driver resources if app fails. Similarly,
-if resourceRetentionPolicy is set to `Always`, operator would not delete driver resources
+if resourceRetainPolicy is set to `Always`, operator would not delete driver resources
 when app ends. Note that this applies only to operator-created resources (driver pod, SparkConf
 configmap .etc). You may also want to tune `spark.kubernetes.driver.service.deleteOnTermination`
 and `spark.kubernetes.executor.deleteOnTermination` to control the behavior of driver-created