Update sympy.ipynb

Author: Tom-van-Woudenberg

book/08/sympy.ipynb

@@ -1509,14 +1509,12 @@
     "## Gotchas\n",
     "Trial and error is an approach for many programmers, but you may want to prevent frequently made mistakes. Take a look at SymPy's documentation on [gotchas](https://docs.sympy.org/latest/tutorials/intro-tutorial/gotchas.html) to accelerate your learning!\n",
     "\n",
-    "````{margin}\n",
     "```{attributiongrey} Attribution\n",
     ":class: attribution\n",
     "Written by Tom van Woudenberg\n",
     "\n",
     "This page reuses CC BY content from {cite:t}`sympy`. {fa}`quote-left`[Find out more here](external_resources)\n",
-    "```\n",
-    "````"
+    "```"
    ]
   }
  ],