[SPARK-54813] Remove cores configs from tests/e2e/watched-namespaces/spark-example.yaml

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

This PR aims to simplify `tests/e2e/watched-namespaces/spark-example.yaml` by removing irrelevant  `spark.kubernetes.*.request.cores` configs and adding relevant `Spark Operator` configuration explicitly.

### Why are the changes needed?

The main consumer of CPU resources is `Spark Operator` instead of `Spark Application`. We had better explicitly set `Spark Operator` CPU core request.

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

No behavior change.

### How was this patch tested?

Pass the CIs.

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

No.

Closes #443 from dongjoon-hyun/SPARK-54813.

Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

Author: dongjoon-hyun

tests/e2e/helm/dynamic-config-values.yaml

@@ -24,6 +24,13 @@ workloadResources:
   roleBinding:
     create: true
 
+operatorDeployment:
+  operatorPod:
+    operatorContainer:
+      resources:
+        requests:
+          cpu: "0.1"
+
 operatorConfiguration:
   dynamicConfig:
     enable: true

tests/e2e/watched-namespaces/spark-example.yaml

@@ -27,7 +27,5 @@ spec:
     spark.executor.instances: "1"
     spark.kubernetes.container.image: "apache/spark:{{SPARK_VERSION}}-scala"
     spark.kubernetes.authenticate.driver.serviceAccountName: "spark"
-    spark.kubernetes.driver.request.cores: "0.5"
-    spark.kubernetes.executor.request.cores: "0.5"
   runtimeVersions:
     sparkVersion: 4.1.0