fix: prevent newline accumulation in XML parameter serialization (#11767)

Co-authored-by: Lai Jinyi <laijinyi@tp-link.com.cn>

openhands/llm/fn_call_converter.py

@@ -421,16 +421,12 @@ def convert_tool_call_to_string(tool_call: dict) -> str:
             f'Failed to parse arguments as JSON. Arguments: {tool_call["function"]["arguments"]}'
         ) from e
     for param_name, param_value in args.items():
-        is_multiline = isinstance(param_value, str) and '\n' in param_value
+        # Don't add extra newlines - keep parameter value as-is
         ret += f'<parameter={param_name}>'
-        if is_multiline:
-            ret += '\n'
         if isinstance(param_value, list) or isinstance(param_value, dict):
             ret += json.dumps(param_value)
         else:
             ret += f'{param_value}'
-        if is_multiline:
-            ret += '\n'
         ret += '</parameter>\n'
     ret += '</function>'
     return ret