Fix type placeholder convention (#1259)

Updated the error message to replace the placeholder `your_type` with
`YourType`, removing the underscore and adopting PascalCase, which
aligns with standard Python type naming conventions.

Author: mshsheikh

src/agents/agent_output.py

@@ -116,7 +116,7 @@ def __init__(self, output_type: type[Any], strict_json_schema: bool = True):
                 raise UserError(
                     "Strict JSON schema is enabled, but the output type is not valid. "
                     "Either make the output type strict, "
-                    "or wrap your type with AgentOutputSchema(your_type, strict_json_schema=False)"
+                    "or wrap your type with AgentOutputSchema(YourType, strict_json_schema=False)"
                 ) from e
 
     def is_plain_text(self) -> bool: