Ensure ecosystem project errors are properly fenced (#8516)

Fixes bug where errors could be unfenced resulting in hidden remaining
content

e.g. https://github.com/astral-sh/ruff/pull/8508#issuecomment-1794960132

python/ruff-ecosystem/ruff_ecosystem/check.py

@@ -200,7 +200,7 @@ def markdown_check_result(result: Result) -> str:
         lines.extend(
             markdown_project_section(
                 title="error",
-                content=f"```\n{error}```",
+                content=f"```\n{str(error).strip()}\n```",
                 options=project.check_options,
                 project=project,
             )