docs: add missing numpy import to minimal example (#39444)

docs: add numpy import to minimal example

docs/source/en/model_doc/timesfm.md

@@ -37,6 +37,7 @@ The original code can be found [here](https://github.com/google-research/timesfm
 To use the model:
 
 ```python
+import numpy as np
 import torch
 from transformers import TimesFmModelForPrediction