fix(eks): incorrect version of aws-node-termination-handler (#19510)

A previous [PR](#18841) upgraded the version of `aws-node-termination-handler`. However, the version contained in the change, 1.14.0, refers to the `appVersion` field and not the `version` field. This change upgrades it to the latest available `version`, 0.18.0, as shown by the command:

```
$ helm search repo aws-node-termination-handler
NAME                            	CHART VERSION	APP VERSION	DESCRIPTION
eks/aws-node-termination-handler	0.18.0       	1.16.0     	A Helm chart for the AWS Node Termination Handler.
```

----

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packages/@aws-cdk/aws-eks/lib/cluster.ts

@@ -946,7 +946,7 @@ abstract class ClusterBase extends Resource implements ICluster {
     if (!this._spotInterruptHandler) {
       this._spotInterruptHandler = this.addHelmChart('spot-interrupt-handler', {
         chart: 'aws-node-termination-handler',
-        version: '1.14.1',
+        version: '0.18.0',
         repository: 'https://aws.github.io/eks-charts',
         namespace: 'kube-system',
         values: {

packages/@aws-cdk/aws-eks/test/integ.eks-cluster.expected.json

@@ -2690,7 +2690,7 @@
         },
         "Release": "ksclustertestclusterchartspotinterrupthandlerf41ba997",
         "Chart": "aws-node-termination-handler",
-        "Version": "1.14.1",
+        "Version": "0.18.0",
         "Values": "{\"nodeSelector\":{\"lifecycle\":\"Ec2Spot\"}}",
         "Namespace": "kube-system",
         "Repository": "https://aws.github.io/eks-charts",