fix(balatrollm): remove hard-coded usage in the DEFAULT_MODEL_CONFIG

This parameter now needs to be set in the config/ file.
That way we can support multiple providers (e.g. Cerebras)
`usage` was a Openrouter-specific parameter.

Author: S1M0N38

src/balatrollm/config.py

@@ -23,9 +23,7 @@
         "HTTP-Referer": "https://github.com/coder/balatrollm",
         "X-Title": "BalatroLLM",
     },
-    "extra_body": {
-        "usage": {"include": True},
-    },
+    "extra_body": {},
 }
 
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