[SPARK-52139] Fix Helm chart icon to use PNG file

Author: dongjoon-hyun

build-tools/helm/spark-kubernetes-operator/Chart.yaml

@@ -18,4 +18,4 @@ description: The official Helm chart to deploy Apache Spark, an unified engine f
 type: application
 version: 1.0.0-dev
 appVersion: 0.2.0-SNAPSHOT
-icon: https://spark.apache.org/favicon.ico
+icon: https://spark.apache.org/images/spark-logo.png