Default to in-cluster API server to init the Kubeflow SDK

Author: astefanutti

examples/kfto-sft-llm/sft.ipynb

@@ -309,7 +309,7 @@
     "from kubeflow.training import TrainingClient\n",
     "from kubeflow.training.models import V1Volume, V1VolumeMount, V1PersistentVolumeClaimVolumeSource\n",
     "\n",
-    "api_server = \"<API_SERVER>\"\n",
+    "api_server = \"https://kubernetes.default.svc\"\n",
     "token = \"<TOKEN>\"\n",
     "\n",
     "configuration = client.Configuration()\n",