refactor: rename part-of label from llm-workflows to ai-ml-pipelines

llm-workflows repo has been phased out. Update labels to reflect
the new ai-ml-pipelines naming convention.

coqui-voice-training.yaml

@@ -9,7 +9,7 @@ metadata:
   namespace: ai-ml
   labels:
     app.kubernetes.io/name: coqui-voice-training
-    app.kubernetes.io/part-of: llm-workflows
+    app.kubernetes.io/part-of: ai-ml-pipelines
 spec:
   entrypoint: train-voice
   serviceAccountName: argo-workflow