fixed the outdated AKS version for eastus2 (#367)

the current latest supported version is 1.25.5. Version 1.25.2 specified in this template is outdated and is not supported. You get the following message if you try to deploy it: 

Inner Errors:
{"code": "AgentPoolK8sVersionNotSupported", "message": "Provisioning of resource(s) for container service aks-66o25hx5ah3mu in resource group rg-bu0001a0008 failed. Message: Version 1.25.2 is not supported in this region. Please use [az aks get-versions] command to get the supported version list in this region. For more information, please check https://aka.ms/supported-version-list. Details: "}

{
      "default": null,
      "isPreview": null,
      "orchestratorType": "Kubernetes",
      "orchestratorVersion": "1.25.5",
      "upgrades": null
    }

cluster-stamp.bicep

@@ -43,7 +43,7 @@ param clusterAuthorizedIPRanges array = []
   'southeastasia'
 ])
 param location string = 'eastus2'
-param kubernetesVersion string = '1.25.2'
+param kubernetesVersion string = '1.25.5'
 
 @description('Domain name to use for App Gateway and AKS ingress.')
 param domainName string = 'contoso.com'