Remove guardian on watsonx recipe from CI

The ibm/granite-guardian-3-8b model is deprecated on Watsonx and will
soon be removed. The recipe is currently failing in the nightly build.

Signed-off-by: BJ Hargrave <hargrave@us.ibm.com>

Author: bjhargrave

.github/notebook_lists/vanilla_notebooks.txt

@@ -14,7 +14,6 @@ recipes/Granite_Guardian/HAP.ipynb
 recipes/Granite_Guardian/Granite_Guardian_Quick_Start.ipynb
 recipes/Granite_Guardian/Granite_Guardian_Detailed_Guide.ipynb
 recipes/Granite_Guardian/Granite_Guardian_Usage_Governance_Workflow.ipynb
-recipes/Granite_Guardian/Granite_Guardian_Watsonx_Usage.ipynb
 recipes/AI-Agents/travel_planner_agent.ipynb
 recipes/Evaluation/Unitxt_Quick_Start.ipynb
 recipes/Evaluation/Unitxt_Demo_Strategies.ipynb