Apply suggestions from code review

Co-authored-by: SamyOubouaziz <[email protected]>

Author: nerda-codes

ai-data/generative-apis/how-to/use-function-calling.mdx

@@ -147,7 +147,7 @@ response = client.chat.completions.create(
 </Message>
 
 <Message type="important">
-    Some models shall be told they can use external functions in the system prompt. If you do not provide a system prompt when using tools, Scaleway will automatically add one that works best for that specific model.
+    Some models must be told they can use external functions in the system prompt. If you do not provide a system prompt when using tools, Scaleway will automatically add one that works best for that specific model.
 </Message>
 
 ### Multi-turn conversation handling