chore: remove unused custom_display_fn from agent.py

- Removed unused custom_display_fn function that was defined but never called
- Cleanup after streaming fix to avoid confusion
- No functional changes, streaming fix remains intact

Co-authored-by: Mervin Praison <MervinPraison@users.noreply.github.com>

Author: github-actions[bot]

src/praisonai-agents/praisonaiagents/agent/agent.py

@@ -1128,11 +1128,6 @@ def _chat_completion(self, messages, temperature=0.2, tools=None, stream=True, r
                     )
             else:
                 # Use the standard OpenAI client approach with tool support
-                def custom_display_fn(text, start_time):
-                    if self.verbose:
-                        return display_generating(text, start_time)
-                    return ""
-                
                 # Note: openai_client expects tools in various formats and will format them internally
                 # But since we already have formatted_tools, we can pass them directly
                 if self._openai_client is None: