Switch to max_completion_tokens for newer OpenAI models

gpt-5-nano and other newer models require max_completion_tokens
instead of max_tokens. The new parameter is backwards compatible
with older models.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bot.py

@@ -146,7 +146,7 @@ class BCSBot(commands.Bot):
             await self.llm._client.chat.completions.create(
                 model=self.llm.model,
                 messages=[{"role": "user", "content": "hi"}],
-                max_tokens=1,
+                max_completion_tokens=1,
             )
             logger.info("LLM connectivity check passed.")
         except Exception as e: