fixup! convert.py: sys.stderr.write --> logger.error

Author: mofosyne

convert.py

@@ -1436,7 +1436,7 @@ def default_outfile(model_paths: list[Path], file_type: GGMLFileType) -> Path:
     if ret in model_paths:
         logger.error(
             f"Error: Default output path ({ret}) would overwrite the input. "
-            "Please explicitly specify a path using --outfile.\n")
+            "Please explicitly specify a path using --outfile.")
         sys.exit(1)
     return ret