docs: Update release notes to include OpenAI tool call execution convenience

Author: rpanackal

docs/release_notes.md

@@ -14,6 +14,7 @@
 
 - [Prompt Registry] [Add Prompt Registry client](https://sap.github.io/ai-sdk/docs/java/ai-core/prompt-registry)
   - `com.sap.ai.sdk:prompt-registry:1.6.0`
+- [OpenAI] [Add convenience for tool call execution](https://sap.github.io/ai-sdk/docs/java/foundation-models/openai/chat-completion#executing-tool-calls)
 
 ### 📈 Improvements