Switch default for ExecConfig api version from v1alpha1->v1beta1

[dims]

fix for errors like these, for example from: (log)[https://productionresultssa1.blob.core.windows.net/actions-results/5e902fd4-9bd9-4c94-9585-48864642edbd/workflow-job-run-2f18dc0c-68b9-5c36-2bef-1c771ed53d83/logs/job/job-logs.txt?rsct=text%2Fplain&se=2025-02-26T14%3A10%3A12Z&sig=7N0spFARzaxDGFWIfgu03p%2B82yaGiTBBJAOdvArNi0Q%3D&ske=2025-02-26T23%3A15%3A16Z&skoid=ca7593d4-ee42-46cd-af88-8b886a2f84eb&sks=b&skt=2025-02-26T11%3A15%3A16Z&sktid=398a6654-997b-47e9-b12b-9515b896b4de&skv=2025-01-05&sp=r&spr=https&sr=b&st=2025-02-26T14%3A00%3A07Z&sv=2025-01-05]

also see report in #8198 (comment)

[0]   [FAILED] Unexpected error:
[0]       <*errors.errorString | 0xc000e59b00>: 
[0]       exec plugin: invalid apiVersion "client.authentication.k8s.io/v1alpha1"
[0]       {
[0]           s: "exec plugin: invalid apiVersion \"client.authentication.k8s.io/v1alpha1\"",
[0]       }

v1alpha1 was removed in k8s 1.24 per CHANGELOG:

The client.authentication.k8s.io/v1alpha1 ExecCredential has been removed. If you are using a client-go credential plugin 
that relies on the v1alpha1 API please contact the distributor of your plugin for instructions on how to migrate to the 
v1 API. (https://github.com/kubernetes/kubernetes/pull/108616, [@margocrawf](https://github.com/margocrawf))