[MINOR] Revise Helm chart README

Author: dongjoon-hyun

build-tools/helm/spark-kubernetes-operator/README.md

@@ -38,7 +38,7 @@ cluster using the [Helm](https://helm.sh) package manager. With this, you can la
 
 ## Features
 
-- Support Apache Spark 3.5 and 4.0 (RC5)
+- Support Apache Spark 3.5+
 - Support `SparkApp` and `SparkCluster` CRDs
   - `sparkapplications.spark.apache.org` (v1alpha1)
   - `sparkclusters.spark.apache.org` (v1alpha1)