Remove warning text

Author: prparker

lecturebook/lecture04/reading-04.ipynb

@@ -3481,19 +3481,12 @@
      "iopub.status.busy": "2025-06-16T15:03:23.011568Z",
      "iopub.status.idle": "2025-06-16T15:03:23.125520Z",
      "shell.execute_reply": "2025-06-16T15:03:23.125261Z"
-    }
+    },
+    "tags": [
+     "hide-input"
+    ]
    },
    "outputs": [
-    {
-     "name": "stderr",
-     "output_type": "stream",
-     "text": [
-      "<>:7: SyntaxWarning: invalid escape sequence '\\m'\n",
-      "<>:7: SyntaxWarning: invalid escape sequence '\\m'\n",
-      "/var/folders/3n/r5vj11ss7lzcdl10vfhb_mw00000gs/T/ipykernel_68920/3227439545.py:7: SyntaxWarning: invalid escape sequence '\\m'\n",
-      "  plt.axvline(x=0, color='r', linestyle='--', label='$\\mathbb{E}[X]$')\n"
-     ]
-    },
     {
      "data": {
       "image/svg+xml": [